Removes rails_6_0.gemfile from CI

Author: ericproulx

.github/workflows/test.yml

@@ -24,7 +24,7 @@ jobs:
       fail-fast: false
       matrix:
         ruby: ['2.7', '3.0', '3.1', '3.2', '3.3']
-        gemfile: [Gemfile, gemfiles/rack_2_0.gemfile, gemfiles/rack_3_0.gemfile, gemfiles/rack_3_1.gemfile, gemfiles/rails_6_0.gemfile, gemfiles/rails_6_1.gemfile, gemfiles/rails_7_0.gemfile, gemfiles/rails_7_1.gemfile, gemfiles/rails_7_2.gemfile, gemfiles/rails_8_0.gemfile]
+        gemfile: [Gemfile, gemfiles/rack_2_0.gemfile, gemfiles/rack_3_0.gemfile, gemfiles/rack_3_1.gemfile, gemfiles/rails_6_1.gemfile, gemfiles/rails_7_0.gemfile, gemfiles/rails_7_1.gemfile, gemfiles/rails_7_2.gemfile, gemfiles/rails_8_0.gemfile]
         specs: ['spec --exclude-pattern=spec/integration/**/*_spec.rb']
         include:
           - ruby: '2.7'