Remove unnecessary bundle lock --add-platform from CI workflow

The x86_64-linux platform is already present in all Gemfile.lock files,
so running 'bundle lock --add-platform' is unnecessary and was causing
the lockfile to be modified during CI runs, particularly on Ruby 2.7.

This fixes the check_react_and_ujs (2.7) test failure.

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

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

Author: justin808

.github/workflows/ruby.yml

@@ -47,7 +47,7 @@ jobs:
           path: vendor/bundle
           key: root-gem-cache-${{ hashFiles('Gemfile.lock') }}
       - name: Install Ruby Gems
-        run: bundle lock --add-platform 'x86_64-linux' && bundle check --path=vendor/bundle || bundle _2.4.9_ install --path=vendor/bundle --jobs=4 --retry=3
+        run: bundle check --path=vendor/bundle || bundle _2.4.9_ install --path=vendor/bundle --jobs=4 --retry=3
       - run: yarn
       - run: bundle exec rake react:update
       - run: bundle exec rake ujs:update
@@ -114,7 +114,7 @@ jobs:
         path: test/dummy/vendor/bundle
         key: dummy-app-gem-cache-${{ hashFiles(format('{0}/gemfiles/{1}.gemfile.lock', github.workspace, matrix.gemfile)) }}
     - name: Install Ruby Gems for dummy app
-      run: bundle lock --add-platform 'x86_64-linux' && bundle check --path=test/dummy/vendor/bundle || bundle _2.4.9_ install --frozen --path=test/dummy/vendor/bundle --jobs=4 --retry=3
+      run: bundle check --path=test/dummy/vendor/bundle || bundle _2.4.9_ install --frozen --path=test/dummy/vendor/bundle --jobs=4 --retry=3
     - run: cd test/dummy && yalc add react_ujs && ${{ matrix.js_package_manager.installer }} install
     - run: bundle exec rake test
       env: