fix warning for ruby 2.6

> bundle install
C:\Windows\system32\cmd.exe /D /S /C "C:\hostedtoolcache\windows\Ruby\2.6.10\x64\bin\bundle.bat config --local path D:\a\ocran\ocran\vendor\bundle"
Your RubyGems version (3.0.3.1) has a bug that prevents `required_ruby_version` from working for Bundler. Any scripts that use `gem install bundler` will break as soon as Bundler drops support for your Ruby version. Please upgrade RubyGems to avoid future breakage and silence this warning by running `gem update --system 3.2.3`
C:\Windows\system32\cmd.exe /D /S /C "C:\hostedtoolcache\windows\Ruby\2.6.10\x64\bin\bundle.bat config --local deployment true"
Your RubyGems version (3.0.3.1) has a bug that prevents `required_ruby_version` from working for Bundler. Any scripts that use `gem install bundler` will break as soon as Bundler drops support for your Ruby version. Please upgrade RubyGems to avoid future breakage and silence this warning by running `gem update --system 3.2.3`
Cache key: setup-ruby-bundler-cache-v6-windows-2022-x64-ruby-2.6.10-wd-D:\a\ocran\ocran-with--without--only--Gemfile.lock-e3ae0a176909bb03fa9d2635acb247f9a64f8374a02f04cb3f4804a16ea94ea4
C:\Windows\system32\cmd.exe /D /S /C "C:\hostedtoolcache\windows\Ruby\2.6.10\x64\bin\bundle.bat install --jobs 4"
Your RubyGems version (3.0.3.1) has a bug that prevents `required_ruby_version` from working for Bundler. Any scripts that use `gem install bundler` will break as soon as Bundler drops support for your Ruby version. Please upgrade RubyGems to avoid future breakage and silence this warning by running `gem update --system 3.2.3`

.github/workflows/test-on-push.yml

@@ -19,6 +19,10 @@ jobs:
           ruby-version: ${{ matrix.ruby }}
           bundler-cache: true
 
+      - name: Update RubyGems (only for Ruby 2.6)
+        run: gem update --system 3.2.3
+        if: matrix.ruby-version == '2.6'
+
       - name: Build stub and run tests 
         run: |
           bundle exec rake build_stub