Bump ruby/setup-ruby from 1.278.0 to 1.281.0

Bumps [ruby/setup-ruby](https://github.com/ruby/setup-ruby) from 1.278.0 to 1.281.0.
- [Release notes](https://github.com/ruby/setup-ruby/releases)
- [Changelog](https://github.com/ruby/setup-ruby/blob/master/release.rb)
- [Commits](ruby/setup-ruby@4c24fa5...675dd7b)

---
updated-dependencies:
- dependency-name: ruby/setup-ruby
  dependency-version: 1.281.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/cibuild.yaml

@@ -14,7 +14,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v6
-      - uses: ruby/setup-ruby@4c24fa5ec04b2e79eb40571b1cee2a0d2b705771 # v1.278.0
+      - uses: ruby/setup-ruby@675dd7ba1b06c8786a1480d89c384f5620a42647 # v1.281.0
         with:
           ruby-version: ${{ matrix.ruby }}
       - name: script/cibuild

.github/workflows/pages-gem.yml

@@ -14,7 +14,7 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v6
       - name: Setup Ruby
-        uses: ruby/setup-ruby@4c24fa5ec04b2e79eb40571b1cee2a0d2b705771 # v1.278.0
+        uses: ruby/setup-ruby@675dd7ba1b06c8786a1480d89c384f5620a42647 # v1.281.0
         with:
           ruby-version: "3.3"
       - name: Build gem