build: bump actions/checkout from 2.3.5 to 2.4.0

Bumps [actions/checkout](https://github.com/actions/checkout) from 2.3.5 to 2.4.0.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@1e204e9...ec3a7ce)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

.github/workflows/ci.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: ubuntu-20.04
 
     steps:
-    - uses: actions/checkout@1e204e9a9253d643386038d443f96446fa156a97 # 2.3.4
+    - uses: actions/checkout@ec3a7ce113134d7a93b817d10a8272cb61118579 # 2.4.0
 
     # Our tests require Nim to be installed to `/nim` because some error messages contain
     # e.g. `/nim/lib/pure/unittest.nim(654)`.
@@ -43,7 +43,7 @@ jobs:
     runs-on: ubuntu-20.04
 
     steps:
-    - uses: actions/checkout@1e204e9a9253d643386038d443f96446fa156a97 # 2.3.4
+    - uses: actions/checkout@ec3a7ce113134d7a93b817d10a8272cb61118579 # 2.4.0
 
     - name: Download all `exercism/nim` exercises
       run: git clone --depth 1 https://github.com/exercism/nim.git

.github/workflows/docker.yml

@@ -14,7 +14,7 @@ jobs:
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@1e204e9a9253d643386038d443f96446fa156a97 # 2.3.4
+        uses: actions/checkout@ec3a7ce113134d7a93b817d10a8272cb61118579 # 2.4.0
 
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@94ab11c41e45d028884a99163086648e898eed25 # 1.6.0

.github/workflows/lint_dockerfile.yml

@@ -7,7 +7,7 @@ jobs:
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@1e204e9a9253d643386038d443f96446fa156a97 # 2.3.4
+        uses: actions/checkout@ec3a7ce113134d7a93b817d10a8272cb61118579 # 2.4.0
 
       - name: Run hadolint
         uses: hadolint/hadolint-action@d7b38582334d9ac11c12021c16f21d63015fa250 # 1.6.0

.github/workflows/shellcheck.yml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ubuntu-20.04
     steps:
       - name: Checkout
-        uses: actions/checkout@1e204e9a9253d643386038d443f96446fa156a97 # 2.3.4
+        uses: actions/checkout@ec3a7ce113134d7a93b817d10a8272cb61118579 # 2.4.0
 
       - name: Run shellcheck
         uses: ludeeus/action-shellcheck@94e0aab03ca135d11a35e5bfc14e6746dc56e7e9 # 1.1.0

.github/workflows/sync-labels.yml

@@ -15,7 +15,7 @@ jobs:
     name: Sync labels
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@1e204e9a9253d643386038d443f96446fa156a97
+      - uses: actions/checkout@ec3a7ce113134d7a93b817d10a8272cb61118579 # 2.4.0
       - uses: micnncim/action-label-syncer@3abd5ab72fda571e69fffd97bd4e0033dd5f495c
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}