Update checkout action version to v4.

.github/workflows/docs-lint.yml

@@ -26,7 +26,7 @@ jobs:
   markdownlint:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
     - uses: ruby/setup-ruby@v1
       with:
         ruby-version: 2.7
@@ -38,7 +38,7 @@ jobs:
   rubocop:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
     - uses: ruby/setup-ruby@v1
       with:
         ruby-version: 2.7
@@ -51,7 +51,7 @@ jobs:
   forspell:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
     - name: Install Hunspell
       run: |
         sudo apt-get install hunspell
@@ -71,7 +71,7 @@ jobs:
   lychee:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
     - name: Link Checker
       id: lychee
       uses: lycheeverse/[email protected]

.github/workflows/rubocop.yml

@@ -11,7 +11,7 @@ jobs:
   rubocop:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
     - uses: ruby/setup-ruby@v1
       with:
         ruby-version: 2.7

.github/workflows/test-jruby.yml

@@ -15,7 +15,7 @@ jobs:
       BUNDLE_RETRY: 3
       CI: true
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
     - uses: actions/cache@v1
       with:
         path: /home/runner/bundle

.github/workflows/test.yml

@@ -42,7 +42,7 @@ jobs:
           gemfile: "gemfiles/rails6.gemfile"
           coverage: "false"
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
     - uses: ruby/setup-ruby@v1
       with:
         ruby-version: ${{ matrix.ruby }}