fix(update): align brew list timeout with file's 5s convention

`_installed_homebrew_version` used a 60s timeout for the local
`brew list --versions` query; the file's other local package-state
queries (dpkg-query, rpm) use 5s. A local DB read never needs 60s, and
a shorter timeout fails fast if brew hangs. Addresses CodeRabbit review.

Author: elkaix

src/pythinker_code/ui/shell/update.py

@@ -665,7 +665,7 @@ def _installed_homebrew_version() -> str | None:
             encoding="utf-8",
             errors="replace",
             env=get_clean_env(),
-            timeout=60,
+            timeout=5,
         )
     except (OSError, subprocess.SubprocessError):
         logger.exception("Failed to read installed Homebrew version:")