⬆️ Bump actions/checkout from 2 to 4 (#408)

Bumps [actions/checkout](https://github.com/actions/checkout) from 2 to 4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v2...v4)

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

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

Author: dependabot[bot]

.github/workflows/cache.yml

@@ -10,7 +10,7 @@ jobs:
       image: ghcr.io/quantecon/lecture-python-container:cuda-12.5.0-anaconda-2024-06-py311
       options: --gpus all
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           ref: ${{ github.event.pull_request.head.sha }}
       - name: Check nvidia drivers

.github/workflows/execution.yml

@@ -14,7 +14,7 @@ jobs:
         python-version: ["3.11"]
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
       - uses: conda-incubator/setup-miniconda@v2
         with:
           auto-update-conda: true
@@ -57,7 +57,7 @@ jobs:
         python-version: ["3.11"]
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
       - uses: conda-incubator/setup-miniconda@v2
         with:
           auto-update-conda: true
@@ -89,7 +89,7 @@ jobs:
   #       python-version: ["3.11"]
   #   steps:
   #     - name: Checkout
-  #       uses: actions/checkout@v2
+  #       uses: actions/checkout@v4
   #     - uses: conda-incubator/setup-miniconda@v2
   #       with:
   #         auto-update-conda: true

.github/workflows/linkcheck.yml

@@ -16,7 +16,7 @@ jobs:
         python-version: ["3.11"]
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
       - name: Setup Anaconda
         uses: conda-incubator/setup-miniconda@v2
         with:

.github/workflows/publish.yml

@@ -12,7 +12,7 @@ jobs:
       options: --gpus all
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
       - name: Install Git (required to commit notebooks)
         shell: bash -l {0}
         run: apt-get install -y git