Update gem-push.yml

Author: strehle

.github/workflows/gem-push.yml

@@ -15,7 +15,7 @@ jobs:
     - name: Set up Ruby 2.6
       uses: actions/setup-ruby@v1
       with:
-        ruby-version: 2.6.x
+        ruby-version: 2.6
 
     - name: Publish to RubyGems
       run: |