Disable rust-analyzer tests on LLVM 21 The rust-analyzer tests have been frequently failing with a SIGSEGV on CI in the LLVM 21 runners. In my investigation, this seems to be fixed with LLVM 22. It was suggested that we should just disable these tests. There wasn't a particularly convenient way to detect if this is running with LLVM 21, so I decided to just check the CI_JOB_NAME which contains the image name which in our case includes the string "llvm-21". Fixes https://github.com/rust-lang/rust/issues/156460