build(deps): bump ruby/setup-ruby from 1.218.0 to 1.221.0 (fluent#4834)

Bumps [ruby/setup-ruby](https://github.com/ruby/setup-ruby) from 1.218.0
to 1.221.0.

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/test-ruby-head.yml

@@ -21,7 +21,7 @@ jobs:
     steps:
       - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
       - name: Set up Ruby
-        uses: ruby/setup-ruby@d781c1b4ed31764801bfae177617bb0446f5ef8d # v1.218.0
+        uses: ruby/setup-ruby@32110d4e311bd8996b2a82bf2a43b714ccc91777 # v1.221.0
         with:
           ruby-version: ${{ matrix.ruby-version }}
       - name: Install addons

.github/workflows/test.yml

@@ -32,7 +32,7 @@ jobs:
     steps:
       - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
       - name: Set up Ruby
-        uses: ruby/setup-ruby@d781c1b4ed31764801bfae177617bb0446f5ef8d # v1.218.0
+        uses: ruby/setup-ruby@32110d4e311bd8996b2a82bf2a43b714ccc91777 # v1.221.0
         with:
           ruby-version: ${{ matrix.ruby-version }}
       - name: Install addons