CI: Drop Ruby 2.7 & 3.0

They are already EOL.

Author: ashie

.github/workflows/linux.yml

@@ -8,7 +8,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: [ '2.7', '3.0', '3.1', '3.2', '3.3', '3.4' ]
+        ruby: [ '3.1', '3.2', '3.3', '3.4' ]
         os: [ 'ubuntu-latest' ]
     name: Ruby ${{ matrix.ruby }} unit testing on ${{ matrix.os }}
     steps:

.github/workflows/windows.yml

@@ -8,7 +8,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: [ '2.7', '3.0', '3.1', '3.2', '3.3', '3.4' ]
+        ruby: [ '3.1', '3.2', '3.3', '3.4' ]
         os: [ 'windows-latest' ]
     name: Ruby ${{ matrix.ruby }} unit testing on ${{ matrix.os }}
     steps: