Bump actions/checkout from 2 to 2.3.4 (#5703)

Bumps [actions/checkout](https://github.com/actions/checkout) from 2 to 2.3.4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v2...v2.3.4)

Signed-off-by: dependabot[bot] <[email protected]>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/ci.yml

@@ -22,7 +22,7 @@ jobs:
     timeout-minutes: 5
     steps:
     - name: Checkout
-      uses: actions/checkout@v2
+      uses: actions/checkout@v2.3.4
       with:
         submodules: true
     - name: Setup Python 3.8
@@ -97,7 +97,7 @@ jobs:
     timeout-minutes: 15
     steps:
     - name: Checkout
-      uses: actions/checkout@v2
+      uses: actions/checkout@v2.3.4
       with:
         submodules: true
     - name: Setup Python ${{ matrix.pyver }}
@@ -150,7 +150,7 @@ jobs:
     needs: pre-deploy
     steps:
     - name: Checkout
-      uses: actions/checkout@v2
+      uses: actions/checkout@v2.3.4
       with:
         submodules: true
     - name: Setup Python 3.8
@@ -183,7 +183,7 @@ jobs:
     needs: pre-deploy
     steps:
     - name: Checkout
-      uses: actions/checkout@v2
+      uses: actions/checkout@v2.3.4
       with:
         submodules: true
     - name: Set up QEMU
@@ -232,7 +232,7 @@ jobs:
     needs: pre-deploy
     steps:
     - name: Checkout
-      uses: actions/checkout@v2
+      uses: actions/checkout@v2.3.4
       with:
         submodules: true
     - name: Setup Python 3.8