Fix tests in CI

Comparing the git output was an idiotic idea if we don't pin the git
version. Since I'm not planning on doing that, lets remove comparing the
output.

Author: vHanda

test/commands/single_commands_test.dart

@@ -33,7 +33,12 @@ void main() {
   for (var command in singleCommandsWithErrorTests) {
     test(
       command,
-      () async => testGitCommand(s, command, shouldReturnError: true),
+      () async => testGitCommand(
+        s,
+        command,
+        shouldReturnError: true,
+        ignoreOutput: true,
+      ),
     );
   }