Update actions/checkout action to v2.4.0

.github/workflows/build.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-20.04
     if: github.repository == 'freeCodeCamp/devdocs'
     steps:
-    - uses: actions/checkout@v2.3.5
+    - uses: actions/checkout@v2.4.0
     - name: Set up Ruby
       uses: ruby/setup-ruby@v1.84.0
       with:

.github/workflows/schedule-doc-report.yml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ubuntu-20.04
     if: github.repository == 'freeCodeCamp/devdocs'
     steps:
-    - uses: actions/checkout@v2.3.5
+    - uses: actions/checkout@v2.4.0
     - name: Set up Ruby
       uses: ruby/setup-ruby@v1.84.0
       with:

.github/workflows/test.yml

@@ -9,7 +9,7 @@ jobs:
   test:
     runs-on: ubuntu-20.04
     steps:
-    - uses: actions/checkout@v2.3.5
+    - uses: actions/checkout@v2.4.0
     - name: Set up Ruby
       uses: ruby/setup-ruby@v1.84.0
       with: