ci: pin actions/checkout to v2 (#541)

.github/workflows/dev-image.yml

@@ -33,7 +33,7 @@ jobs:
     runs-on: ubuntu-18.04
     if: contains(github.event.head_commit.message, '[skip ci]') == false
     steps:
-      - uses: actions/checkout@v2.3.1
+      - uses: actions/checkout@v2
       - name: Login to Packages
         run: echo '${{ secrets.GITHUB_TOKEN }}' | docker login 'docker.pkg.github.com' -u 'peaceiris' --password-stdin
       - run: docker-compose pull --quiet

.github/workflows/release.yml

@@ -9,7 +9,7 @@ jobs:
   release:
     runs-on: ubuntu-18.04
     steps:
-      - uses: actions/checkout@v2.3.1
+      - uses: actions/checkout@v2
       - uses: peaceiris/workflows/create-release-npm@v0.7.0
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

.github/workflows/test.yml

@@ -22,7 +22,7 @@ jobs:
           - 'macos-latest'
           - 'windows-latest'
     steps:
-      - uses: actions/checkout@v2.3.1
+      - uses: actions/checkout@v2
 
       - name: Dump GitHub context
         env:

.github/workflows/update-major-tag.yml

@@ -9,7 +9,7 @@ jobs:
     runs-on: ubuntu-18.04
     steps:
 
-    - uses: actions/checkout@v2.3.1
+    - uses: actions/checkout@v2
 
     - name: Update major tag
       if: github.event.release.prerelease == false