fix: catch exceptions.RefreshError (#508)

diff --git a/google/oauth2/id_token.py b/google/oauth2/id_token.py
index f559c6c..e78add4 100644
--- a/google/oauth2/id_token.py
+++ b/google/oauth2/id_token.py
@@ -212,7 +212,7 @@
         )
         credentials.refresh(request)
         return credentials.token
-    except (ImportError, exceptions.TransportError):
+    except (ImportError, exceptions.TransportError, exceptions.RefreshError):
         pass
 
     # 2. Try to use service account credentials to get ID token.