fix(workflow): actions/setup-ruby@v1 is deprecated

Run actions/setup-ruby@v1
------------------------
NOTE: This action is deprecated and is no longer maintained.
Please, migrate to https://github.com/ruby/setup-ruby, which is being actively maintained.
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Error: Version 2.6.x not found

.github/workflows/gem-push.yml

@@ -14,11 +14,10 @@ jobs:
       packages: write
 
     steps:
-    - uses: actions/checkout@v2
-    - name: Set up Ruby 2.6
-      uses: actions/setup-ruby@v1
+    - uses: actions/checkout@v3
+    - uses: ruby/setup-ruby@v1
       with:
-        ruby-version: 2.6.x
+        ruby-version: 3.1
 
     - name: Publish to RubyGems
       run: |

.github/workflows/ubuntu.yml

@@ -13,16 +13,12 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        ruby-version: ['2.5.1', '2.6', '2.7', '3.0']
+        ruby-version: ['2.5.1', '2.6', '2.7', '3.0', '3.1']
         os: [ubuntu-latest]
 
     steps:
-    - uses: actions/checkout@v2
-    - name: Set up Ruby
-    # To automatically get bug fixes and new Ruby versions for ruby/setup-ruby,
-    # change this to (see https://github.com/ruby/setup-ruby#versioning):
-    # uses: ruby/setup-ruby@v1
-      uses: ruby/setup-ruby@473e4d8fe5dd94ee328fdfca9f8c9c7afc9dae5e
+    - uses: actions/checkout@v3
+    - uses: ruby/setup-ruby@v1
       with:
         ruby-version: ${{ matrix.ruby-version }}
         bundler-cache: true # runs 'bundle install' and caches installed gems automatically