Bump actions/checkout from 2 to 2.3.4

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](https://github.com/actions/checkout/compare/v2...v2.3.4)

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

.github/workflows/ci-workflow.yml

@@ -14,7 +14,7 @@ jobs:
   housekeeping:
     runs-on: ubuntu-16.04
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v2.3.4
 
     - name: Set up Python
       uses: actions/setup-python@v2.2.2
@@ -55,7 +55,7 @@ jobs:
       matrix:
         python-version: [3.6, 3.7, 3.8, 3.9]
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v2.3.4
 
     - uses: actions/setup-python@v2.2.2
       with:

.github/workflows/configlet.yml

@@ -7,7 +7,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f
+    - uses: actions/checkout@v2.3.4
 
     - name: Fetch configlet
       uses: exercism/github-actions/configlet-ci@main

.github/workflows/test-runner.yml

@@ -10,6 +10,6 @@ jobs:
   test-runner:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v2.3.4
       - name: Run test-runner
         run: docker-compose run test-runner