update RubyGems in Github Workflow

Author: anoworl

.github/workflows/pull_request.yml

@@ -18,4 +18,5 @@ jobs:
         with:
           ruby-version:  ${{ matrix.ruby_version }}
           bundler-cache: true
-      - run: bundle exec rake
+      - run: gem update --system
+      - run: bundle exec rake

.github/workflows/release.yml

@@ -13,6 +13,7 @@ jobs:
       - uses: ruby/setup-ruby@v1
         with:
           bundler-cache: true
+      - run: gem update --system
       - run: bundle exec rake build
       - id: gem
         run: echo "result=$(find pkg -name 'deploygate-*.gem' -type f | head -1)" >> $GITHUB_OUTPUT