Add gemfiles/.bundle/ to .gitignore

Bundler creates a .bundle config directory relative to BUNDLE_GEMFILE
location. Added gemfiles/.bundle/ to .gitignore to prevent CI check
from failing due to untracked files when using ruby27.gemfile.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: justin808

.gitignore

@@ -11,3 +11,4 @@ coverage/
 yalc.lock
 /vendor/bundle
 .bundle/config
+gemfiles/.bundle/