tests: Make ReviewableBranchTests.test_smoke work with git < 2.28.0

Bug: https://crbug.com/gerrit/14380
Change-Id: Id015bd98b008e1530ada2c7e4332c67e8e208e25
Signed-off-by: Peter Kjellerstedt <peter.kjellerstedt@axis.com>
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/303325
Reviewed-by: Mike Frysinger <vapier@google.com>
diff --git a/tests/test_project.py b/tests/test_project.py
index 7dfbabb..9b2cc4e 100644
--- a/tests/test_project.py
+++ b/tests/test_project.py
@@ -46,7 +46,7 @@
       templatedir = tempfile.mkdtemp(prefix='.test-template')
       with open(os.path.join(templatedir, 'HEAD'), 'w') as fp:
         fp.write('ref: refs/heads/main\n')
-      cmd += ['--template=', templatedir]
+      cmd += ['--template', templatedir]
     subprocess.check_call(cmd, cwd=tempdir)
     yield tempdir
   finally: