Stop building carbon-explorer from compiler-workflows (#35)

The carbon-explorer is frozen and has been moved out of the
main carbon-lang repo. We can keep serving an old build, but
there's no need to keep building it from the archived repo.

See #7550 and carbon-language/carbon-lang#5270

Author: danakj

.github/workflows/build-daily-carbon.yml

@@ -5,7 +5,6 @@
 * [![Status](https://github.com/compiler-explorer/compiler-workflows/actions/workflows//build-daily-arm64.yml/badge.svg)](https://github.com/compiler-explorer/compiler-workflows/actions/workflows//build-daily-arm64.yml)![Last success](https://img.shields.io/badge/dynamic/json?color=success&label=Last+OK&query=%24.last_success.timestamp&url=https%3A%2F%2Flambda.compiler-explorer.com%2Fcompiler-build%2Farm64)![Last build](https://img.shields.io/badge/dynamic/json?color=yellow&label=Last+build&query=%24.last_build.timestamp&url=https%3A%2F%2Flambda.compiler-explorer.com%2Fcompiler-build%2Farm64)
 * [![Status](https://github.com/compiler-explorer/compiler-workflows/actions/workflows//build-daily-bpf.yml/badge.svg)](https://github.com/compiler-explorer/compiler-workflows/actions/workflows//build-daily-bpf.yml)![Last success](https://img.shields.io/badge/dynamic/json?color=success&label=Last+OK&query=%24.last_success.timestamp&url=https%3A%2F%2Flambda.compiler-explorer.com%2Fcompiler-build%2Fbpf)![Last build](https://img.shields.io/badge/dynamic/json?color=yellow&label=Last+build&query=%24.last_build.timestamp&url=https%3A%2F%2Flambda.compiler-explorer.com%2Fcompiler-build%2Fbpf)
 * [![Status](https://github.com/compiler-explorer/compiler-workflows/actions/workflows//build-daily-c2rust.yml/badge.svg)](https://github.com/compiler-explorer/compiler-workflows/actions/workflows//build-daily-c2rust.yml)![Last success](https://img.shields.io/badge/dynamic/json?color=success&label=Last+OK&query=%24.last_success.timestamp&url=https%3A%2F%2Flambda.compiler-explorer.com%2Fcompiler-build%2Fc2rust)![Last build](https://img.shields.io/badge/dynamic/json?color=yellow&label=Last+build&query=%24.last_build.timestamp&url=https%3A%2F%2Flambda.compiler-explorer.com%2Fcompiler-build%2Fc2rust)
-* [![Status](https://github.com/compiler-explorer/compiler-workflows/actions/workflows//build-daily-carbon.yml/badge.svg)](https://github.com/compiler-explorer/compiler-workflows/actions/workflows//build-daily-carbon.yml)![Last success](https://img.shields.io/badge/dynamic/json?color=success&label=Last+OK&query=%24.last_success.timestamp&url=https%3A%2F%2Flambda.compiler-explorer.com%2Fcompiler-build%2Fcarbon)![Last build](https://img.shields.io/badge/dynamic/json?color=yellow&label=Last+build&query=%24.last_build.timestamp&url=https%3A%2F%2Flambda.compiler-explorer.com%2Fcompiler-build%2Fcarbon)
 * [![Status](https://github.com/compiler-explorer/compiler-workflows/actions/workflows//build-daily-cc65.yml/badge.svg)](https://github.com/compiler-explorer/compiler-workflows/actions/workflows//build-daily-cc65.yml)![Last success](https://img.shields.io/badge/dynamic/json?color=success&label=Last+OK&query=%24.last_success.timestamp&url=https%3A%2F%2Flambda.compiler-explorer.com%2Fcompiler-build%2Fcc65)![Last build](https://img.shields.io/badge/dynamic/json?color=yellow&label=Last+build&query=%24.last_build.timestamp&url=https%3A%2F%2Flambda.compiler-explorer.com%2Fcompiler-build%2Fcc65)
 * [![Status](https://github.com/compiler-explorer/compiler-workflows/actions/workflows//build-daily-circt_trunk.yml/badge.svg)](https://github.com/compiler-explorer/compiler-workflows/actions/workflows//build-daily-circt_trunk.yml)![Last success](https://img.shields.io/badge/dynamic/json?color=success&label=Last+OK&query=%24.last_success.timestamp&url=https%3A%2F%2Flambda.compiler-explorer.com%2Fcompiler-build%2Fcirct_trunk)![Last build](https://img.shields.io/badge/dynamic/json?color=yellow&label=Last+build&query=%24.last_build.timestamp&url=https%3A%2F%2Flambda.compiler-explorer.com%2Fcompiler-build%2Fcirct_trunk)
 * [![Status](https://github.com/compiler-explorer/compiler-workflows/actions/workflows//build-daily-clad.yml/badge.svg)](https://github.com/compiler-explorer/compiler-workflows/actions/workflows//build-daily-clad.yml)![Last success](https://img.shields.io/badge/dynamic/json?color=success&label=Last+OK&query=%24.last_success.timestamp&url=https%3A%2F%2Flambda.compiler-explorer.com%2Fcompiler-build%2Fclad)![Last build](https://img.shields.io/badge/dynamic/json?color=yellow&label=Last+build&query=%24.last_build.timestamp&url=https%3A%2F%2Flambda.compiler-explorer.com%2Fcompiler-build%2Fclad)

build-status.md

@@ -77,7 +77,6 @@ compilers:
     # - { image: clang, name: dang, args: dang-main }
 
     - { image: clang, name: widberg, args: widberg-main }
-    - { image: carbon, name: carbon }
     - { image: ispc, name: ispc }
 
     # See https://github.com/compiler-explorer/compiler-explorer/issues/6828