removing eol 2.7 from CI matrix testing

Author: perryqh

.github/workflows/ci.yml

@@ -8,7 +8,6 @@ jobs:
     strategy:
       matrix:
         ruby:
-          - 2.7
           # See comment comes from https://github.com/ruby/setup-ruby#matrix-of-ruby-versions
           # Due to https://github.com/actions/runner/issues/849, we have to use quotes for '3.0'
           - '3.0'