ci: workaround for an llvm install issue

Solution based on commits in:
llvm/llvm-project#64182

This should be reverted once that issue is resolved (looks like the
maintainer is traveling right now).

.github/workflows/deps.py

@@ -95,6 +95,7 @@ def apt_install(args: argparse.Namespace) -> None:
 
 def install_llvm() -> None:
     run(["wget", "-O", "/tmp/llvm.sh", "https://apt.llvm.org/llvm.sh"])
+    run(["sudo", "apt-get", "purge", "--auto-remove", "llvm", "python3-lldb-14", "llvm-14", "-y"])
     run(["sudo", "bash", "/tmp/llvm.sh"])
     for binary in os.scandir("/usr/bin"):
         if binary.name.startswith("clang-") or binary.name.startswith("clang++-"):