ci ubuntu: Use Ubuntu 24.04 to build released gem

Because libyaml on Ubuntu 22.04 is old.

See also:
9ca7b07#commitcomment-143089497

> The libyaml on Ubuntu 22.04 is outdated a little.
>
> It results in different metadata in the built gems from the latest
> libyaml.

Author: kou

.github/workflows/ubuntu.yml

@@ -19,6 +19,7 @@ jobs:
       fail-fast: false
       matrix:
         os:
+        - ubuntu-24.04
         - ubuntu-22.04
         - ubuntu-20.04
         ruby: ${{ fromJson(needs.ruby-versions.outputs.versions) }}
@@ -40,7 +41,7 @@ jobs:
       run: bundle exec rake build
     - uses: actions/upload-artifact@v4
       if: >-
-        matrix.os == 'ubuntu-22.04' &&
+        matrix.os == 'ubuntu-24.04' &&
           (matrix.ruby == needs.ruby-versions.outputs.latest || matrix.ruby == 'jruby-head')
       with:
         name: gem-${{ matrix.os }}-${{ matrix.ruby }}