Test against Ruby 3.3 in CI

Since Ruby 3.3 is the default Ruby version when using the
`ruby` / `ruby@3` Homebrew package aliases, so has a high
chance of being what people are now using locally.

.github/workflows/ci.yml

@@ -14,7 +14,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby-version: ["2.7", "3.0", "3.1", "3.2"]
+        ruby-version: ["2.7", "3.0", "3.1", "3.2", "3.3"]
     runs-on: ubuntu-22.04
     env:
       HATCHET_APP_LIMIT: 100