Revert "workflows/code.yml: list ruby version to 2.5"

This reverts commit 509c2ad.

Signed-off-by: Philip Li <philip.li@intel.com>

Author: rli9

.github/workflows/code.yml

@@ -22,7 +22,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        ruby-version: ['2.5']
+        ruby-version: ['2.5', '2.6', '2.7', '3.0']
 
     steps:
     - uses: actions/checkout@v3