Fix YAML alias parsing in RSpec bundler tests

Enable alias parsing in YAML.load_file to support shakapacker.yml
which uses YAML anchors (&default) and aliases (<<: *default).

This fixes Psych::AliasesNotEnabled errors in CI.

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

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

Author: justin808

spec/webpack/bundler_switching_spec.rb

@@ -5,7 +5,7 @@
 
 RSpec.describe 'Bundler Switching', type: :feature do
   let(:shakapacker_config_path) { Rails.root.join('config', 'shakapacker.yml') }
-  let(:original_config) { YAML.load_file(shakapacker_config_path) }
+  let(:original_config) { YAML.load_file(shakapacker_config_path, aliases: true) }
 
   after do
     # Restore original config after each test