fix: fix default value

Author: judahrand

google/auth/compute_engine/_metadata.py

@@ -54,7 +54,9 @@
 # Timeout in seconds to wait for the GCE metadata server when detecting the
 # GCE environment.
 try:
-    _METADATA_DEFAULT_TIMEOUT = int(os.getenv(environment_vars.GCE_METADATA_TIMEOUT, 3))
+    _METADATA_DEFAULT_TIMEOUT = int(
+        os.getenv(environment_vars.GCE_METADATA_TIMEOUT, "3")
+    )
 except ValueError:  # pragma: NO COVER
     _METADATA_DEFAULT_TIMEOUT = 3