Remove gitc support from repo

gitc is no longer available.

Change-Id: I0cbfdf936832f2cdd4876104ae3cc5a6e26154e2
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/444841
Reviewed-by: Gavin Mak <gavinmak@google.com>
Commit-Queue: Josip Sokcevic <sokcevic@google.com>
Tested-by: Josip Sokcevic <sokcevic@google.com>

main.py

@@ -45,7 +45,6 @@ from command import InteractiveCommand
 from command import MirrorSafeCommand
 from editor import Editor
 from error import DownloadError
-from error import GitcUnsupportedError
 from error import InvalidProjectGroupsError
 from error import ManifestInvalidRevisionError
 from error import ManifestParseError
@@ -308,10 +307,6 @@ class _Repo:
                 outer_client=outer_client,
             )
 
-        if Wrapper().gitc_parse_clientdir(os.getcwd()):
-            logger.error("GITC is not supported.")
-            raise GitcUnsupportedError()
-
         try:
             cmd = self.commands[name](
                 repodir=self.repodir,