Update gempush.yml

Author: erwanlr

.github/workflows/gempush.yml

@@ -11,10 +11,10 @@ jobs:
 
     steps:
     - uses: actions/checkout@master
-    - name: Set up Ruby 2.7
+    - name: Set up Ruby 3.0
       uses: ruby/setup-ruby@v1
       with:
-        ruby-version: '2.7'
+        ruby-version: '3.0'
         bundler-cache: true
 
     #- name: Publish to GPR