ci: set specific version of actions

It should be updated regularly by dependabot.

Signed-off-by: Kentaro Hayashi <hayashi@clear-code.com>

Author: kenhys

.github/workflows/linux-test.yaml

@@ -22,9 +22,9 @@ jobs:
 
     name: Ruby ${{ matrix.ruby-version }} capability ${{ matrix.capability }} on ${{ matrix.os }}
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@692973e3d937129bcbf40652eb9f2f61becf3332 # v4.1.7
       - name: Set up Ruby
-        uses: ruby/setup-ruby@v1
+        uses: ruby/setup-ruby@a6b46b8a08edb18935835849f2a17072d5cc8c73 # v1.192.0
         with:
           ruby-version: ${{ matrix.ruby-version }}
       - name: Install dependencies