[env] Remove git config for now (#1884)

## Summary
Forgot to remove this in #1869 last night! Too much of a performance hit
on the main thread. We can bring it back via an async thread on startup.

codex-rs/mcp-server/tests/send_message.rs

@@ -99,7 +99,7 @@ async fn test_send_message_success() {
         response
     );
     // wait for the server to hear the user message
-    sleep(Duration::from_secs(10));
+    sleep(Duration::from_secs(5));
 
     // Ensure the server and tempdir live until end of test
     drop(server);