Stop testing Ruby 3.0

Ruby 3.0 is end of life and the async gem is not compatible with it.

Author: sbscully

.github/workflows/build.yml

@@ -13,7 +13,7 @@ jobs:
       matrix:
         os: [ubuntu-latest]
         # https://www.ruby-lang.org/en/downloads/branches/
-        ruby: ["3.0", "3.1", "3.2", "3.3"]
+        ruby: ["3.1", "3.2", "3.3"]
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v4