Update actions/checkout requirement to v2.3.1

Updates the requirements on [actions/checkout](https://github.com/actions/checkout) to permit the latest version.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](https://github.com/actions/checkout/commits/28c7f3d2b5162b5ddd3dfd9a45aa55eaf396478b)

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/integration.yml

@@ -22,7 +22,7 @@ jobs:
     #       - 636:636
 
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v2.3.1
       - uses: actions/setup-node@v1
 
       # Hack way to start service since GitHub doesn't integrate with its own services

.github/workflows/main.yml

@@ -11,7 +11,7 @@ jobs:
     name: Lint Check
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v2.3.1
       - uses: actions/setup-node@v1
       - name: Install Packages
         run: npm install
@@ -32,7 +32,7 @@ jobs:
           - 14.x
     runs-on: ${{ matrix.os }}
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v2.3.1
       - uses: actions/setup-node@v1
         with:
           node-version: ${{ matrix.node }}