Revert "Pin stable to 1.94 for tokio-1.51.x" (#8106)

As we are merging tokio-1.51.x into tokio-1.52.x and then master, we
should not include this change.

This reverts commit bde3f20.

Author: Darksonn

.github/workflows/ci.yml

@@ -15,7 +15,7 @@ env:
   RUST_BACKTRACE: 1
   RUSTUP_WINDOWS_PATH_ADD_BIN: 1
   # Change to specific Rust release to pin
-  rust_stable: 1.94
+  rust_stable: stable
   rust_nightly: nightly-2025-10-12
   # Pin a specific miri version
   rust_miri_nightly: nightly-2025-11-13