Update staging.yml

update ruby version in order to install up-to-date dependencies with fewer vulnearbilities

.github/workflows/staging.yml

@@ -37,13 +37,13 @@ jobs:
       run: |
         python -m pip install --upgrade pip
         pip install -r scripts/requirements.txt
-    - name: Install Ruby 2.6
+    - name: Install Ruby 3.0
       uses: ruby/setup-ruby@v1
       with:
-        ruby-version: '2.6'
+        ruby-version: '3.0'
     - name: Install ruby dependencies
       run: |
-        gem install bundler -v 2.4.22
+        gem install bundler
         bundle
     - name: Set up AWS credentials (+ set default user)
       run: |