Bump actions/checkout from 5 to 6 (#136)

Author: dependabot[bot]

.github/workflows/CI.yml

@@ -36,7 +36,7 @@ jobs:
       PYTEST_ARGS: -v -nauto --cov=openforcefields --cov-config=setup.cfg --cov-append --cov-report=xml
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       - name: Install dependencies
         if: ${{ matrix.toolkit == true }}

.github/workflows/canary.yaml

@@ -24,7 +24,7 @@ jobs:
           - os: macOS-latest
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0