Rust: remove DEP_UPB_VERSION check in codegen crate (#22764)

This check was meant to enforce that the version of the protobuf crate exactly
matches the version of the codegen crate, but this is not strictly necessary.
Tonic would also like to re-export our crate from the `tonic-protobuf` crate,
and the `DEP_UPB_VERSION` check is causing problems with that since the
environment variable is set only for crates that directly depend on the
`protobuf` crate (see
[discussion](hyperium/tonic#2320 (comment))).

While I was at it I also removed the code in the protobuf build script that
sets the `DEP_UPB_INCLUDE` variable, which is unnecessary now that we no longer
generate any C code which would need to know where to find upb's headers.

PiperOrigin-RevId: 786760264

Author: Adam Cozzette

rust/release_crates/protobuf/build.rs

@@ -19,9 +19,4 @@ fn main() {
         .file("libupb/third_party/utf8_range/utf8_range.c")
         .define("UPB_BUILD_API", Some("1"))
         .compile("libupb");
-
-    let path = std::path::absolute("libupb").expect("Failed to get full path to libupb");
-
-    println!("cargo:include={}", path.display());
-    println!("cargo:version={}", VERSION);
 }

rust/release_crates/protobuf_codegen/src/lib.rs

@@ -131,14 +131,6 @@ impl CodeGen {
     }
 
     pub fn generate_and_compile(&self) -> Result<(), String> {
-        let upb_version = std::env::var("DEP_UPB_VERSION").expect("DEP_UPB_VERSION should have been set, make sure that the Protobuf crate is a dependency");
-        if VERSION != upb_version {
-            panic!(
-                "protobuf-codegen version {} does not match protobuf version {}.",
-                VERSION, upb_version
-            );
-        }
-
         let mut version_cmd = std::process::Command::new("protoc");
         let output = version_cmd.arg("--version").output().map_err(|e| {
             format!("failed to run protoc --version: {} {}", e, missing_protoc_error_message())