ci: add more ruby versions

Signed-off-by: Kentaro Hayashi <hayashi@clear-code.com>

Author: kenhys

.github/workflows/linux.yml

@@ -10,9 +10,11 @@ jobs:
       matrix:
         ruby:
           - 2.7
-          - 3.0
+          - "3.0"
           - 3.1
           - 3.2
+          - 3.3
+          - 3.4
         os:
           - ubuntu-latest
     name: Ruby ${{ matrix.ruby }} unit testing on ${{ matrix.os }}