Turn off automatic gemini summary and code review of PRs (#8621)

We can do this locally in gemini CLI if desired without cluttering up PR
comments.

Author: helin24

.gemini/config.yaml

@@ -6,8 +6,8 @@ code_review:
   max_review_comments: -1
   pull_request_opened:
     help: false
-    summary: true
-    code_review: true
+    summary: false
+    code_review: false
     include_drafts: true
 ignore_patterns: []