Update checkout and setup-python actions in CI (#364)

## Description

<!-- Provide a brief description of the PR's purpose here. -->

setup-python and checkout are both at v4 now; the current version of
setup-python (v2) was raising deprecation warnings in GitHub Actions.
This PR upgrades both of these actions.

## TODO

<!-- Notable points that this PR has either accomplished or will
accomplish. -->

## Questions

<!-- Any concerns or points of confusion? -->

## Status

- [x] I have read the guidelines in

[CONTRIBUTING.md](https://github.com/icaros-usc/pyribs/blob/master/CONTRIBUTING.md)
- [x] I have formatted my code using `yapf`
- [x] I have tested my code by running `pytest`
- [x] I have linted my code with `pylint`
- [N/A] I have added a one-line description of my change to the
changelog in
      `HISTORY.md`
- [x] This PR is ready to go

.github/workflows/testing.yml

@@ -18,8 +18,8 @@ jobs:
       # perfectly passes pylint.
       SKIP: pylint
     steps:
-      - uses: actions/checkout@v3
-      - uses: actions/setup-python@v3
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v4
         with:
           python-version: 3.11
       - name: Install all deps and pylint (to be available to pre-commit)
@@ -41,9 +41,9 @@ jobs:
             python-version: "3.10"
     runs-on: ${{ matrix.os }}
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Set up Python ${{ matrix.python-version }}
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v4
         with:
           python-version: ${{ matrix.python-version }}
       - name: Upgrade pip
@@ -56,9 +56,9 @@ jobs:
   pin:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Set up Python 3.8
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v4
         with:
           python-version: "3.8"
       - name: Upgrade pip
@@ -79,9 +79,9 @@ jobs:
   coverage:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Set up Python 3.8
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v4
         with:
           python-version: "3.8"
       - name: Upgrade pip
@@ -99,9 +99,9 @@ jobs:
   benchmarks:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Set up Python 3.8
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v4
         with:
           python-version: "3.8"
       - name: Upgrade pip
@@ -113,9 +113,9 @@ jobs:
   examples:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Set up Python 3.8
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v4
         with:
           python-version: "3.8"
       - name: Upgrade pip
@@ -128,9 +128,9 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       # We use Python 3.10 instead of 3.8 here since Google Colab uses 3.10.
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Set up Python 3.10
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v4
         with:
           python-version: "3.10"
       - name: Upgrade pip
@@ -142,9 +142,9 @@ jobs:
   docs:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Set up Python 3.8
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v4
         with:
           python-version: "3.8"
       - name: Upgrade pip
@@ -158,9 +158,9 @@ jobs:
     needs: [pre-commit, test, pin, coverage, benchmarks, examples, tutorials]
     if: startsWith(github.ref, 'refs/tags')
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Set up Python 3.8
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v4
         with:
           python-version: "3.8"
       - name: Upgrade pip