[git_auth] Remove unnecessary quotes

Not needed with future import

Change-Id: I14d56465dc42ac710b64b301928057329ac9d038
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/5762789
Commit-Queue: Allen Li <ayatane@chromium.org>
Reviewed-by: Yiwei Zhang <yiwzhang@google.com>

git_auth.py

@@ -76,7 +76,7 @@ class ConfigChanger(object):
         return parts._replace(path='/', query='', fragment='').geturl()
 
     @classmethod
-    def new_from_env(cls, cwd: str, cl: git_cl.Changelist) -> 'ConfigChanger':
+    def new_from_env(cls, cwd: str, cl: git_cl.Changelist) -> ConfigChanger:
         """Create a ConfigChanger by inferring from env.
 
         The Gerrit host is inferred from the current repo/branch.