umu_runtime: remove the old runtime after installing the latest

- Always remove the old runtime directory after installing the latest runtime. We want user's to always be using the latest runtime and Proton, and this avoids bloating the user's home directory. However, in the next release, the old runtime directory which should be sniper_platform_0.20240125.75305 will remain as the BUILD_ID.txt file did not exist at the time of the RC4 release, so users would need to manually remove it. Also note that the removal will raise an exception if the runtime directory is a symbolic link presumably due to shutil.rmtree protecting against symbolic link attacks, so users should not be creating links for this directory.

umu/umu_runtime.py

@@ -264,6 +264,7 @@ def _update_umu(
         )
         for file in local.glob(f"*{build_id}"):
             runtime = file
+            log.debug("Runtime: %s", runtime.name)
             break
 
     if (
@@ -326,6 +327,8 @@ def _update_umu(
     ):
         log.console(f"Updating {codename} to latest...")
         _install_umu(json, thread_pool)
+        log.debug("Removing: %s", runtime)
+        rmtree(runtime.as_posix())
         return
     log.console(f"{codename} is up to date")