Bump actions/checkout from 2 to 3

Bumps [actions/checkout](https://github.com/actions/checkout) from 2 to 3.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v2...v3)

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

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

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -19,7 +19,7 @@ jobs:
           - os: ubuntu-latest
             python-version: 3.7
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - name: Setup Python environment
         uses: actions/setup-python@v2.2.2
         with:
@@ -40,7 +40,7 @@ jobs:
   Docs:
     runs-on: macos-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - name: Setup Python environment
         uses: actions/setup-python@v2.2.2
         with:
@@ -73,7 +73,7 @@ jobs:
             - os: ubuntu-latest
               python-version: 3.7
     steps: 
-      - uses: actions/checkout@v2.3.4
+      - uses: actions/checkout@v3
       - name: Setup Python environment
         uses: actions/setup-python@v2.2.2
         with:

.github/workflows/coverage.yml

@@ -11,7 +11,7 @@ jobs:
   Coverage:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - name: Setup Python environment
         uses: actions/setup-python@v2.2.2
         with:
@@ -35,7 +35,7 @@ jobs:
   IntegrationCoverage:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - name: Setup Python environment
         uses: actions/setup-python@v2.2.2
         with:

.github/workflows/pypiupload.yml

@@ -15,7 +15,7 @@ jobs:
         python-version: [2.7, 3.x]
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
     - name: Setup Python
       uses: actions/setup-python@v2.2.2
       with:

.github/workflows/spec_update.yml

@@ -8,7 +8,7 @@ jobs:
   Update:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - name: Setup Python environment
         uses: actions/setup-python@v2.2.2
         with: