Update gem-push.yml

Author: strehle

.github/workflows/gem-push.yml

@@ -13,9 +13,9 @@ jobs:
     steps:
     - uses: actions/checkout@v3
     - name: Set up Ruby 2.6
-      uses: actions/setup-ruby@v1
+      uses: ruby/setup-ruby@v1
       with:
-        ruby-version: 2.6
+        ruby-version: '2.6'
 
     - name: Publish to RubyGems
       run: |