Pin setup-ruby revision for debug

Even if recommended by upstream for using relaxed reference, pinning is useful for debugging
See #425 for detail

Author: kachick

.github/workflows/ci-ruby.yml

@@ -42,7 +42,7 @@ jobs:
       BUNDLE_WITHOUT: development
     steps:
       - uses: actions/checkout@v6
-      - uses: ruby/setup-ruby@v1
+      - uses: ruby/setup-ruby@90be1154f987f4dc0fe0dd0feedac9e473aa4ba8 # v1.286.0
         with:
           ruby-version: ${{ matrix.ruby }}
           # Enabling is the recommended way, but it cannot detect runner changes in early stage.
@@ -55,7 +55,7 @@ jobs:
     runs-on: 'ubuntu-24.04'
     steps:
       - uses: actions/checkout@v6
-      - uses: ruby/setup-ruby@v1
+      - uses: ruby/setup-ruby@90be1154f987f4dc0fe0dd0feedac9e473aa4ba8 # v1.286.0
         with:
           bundler-cache: true
       - run: bundle exec rake rubocop

.github/workflows/release.yml

@@ -27,7 +27,7 @@ jobs:
     runs-on: 'ubuntu-24.04'
     steps:
       - uses: actions/checkout@v6
-      - uses: ruby/setup-ruby@v1
+      - uses: ruby/setup-ruby@90be1154f987f4dc0fe0dd0feedac9e473aa4ba8 # v1.286.0
         with:
           bundler-cache: true
       - run: mkdir -p pkg
@@ -84,7 +84,7 @@ jobs:
     steps:
       - uses: actions/checkout@v6
       - name: Set up Ruby
-        uses: ruby/setup-ruby@v1
+        uses: ruby/setup-ruby@90be1154f987f4dc0fe0dd0feedac9e473aa4ba8 # v1.286.0
         with:
           bundler-cache: false # Don't enable while using .bundle/config. See https://github.com/kachick/rspec-matchers-power_assert_matchers/issues/223#issuecomment-2562853948
       - run: bundle install