Bump actions/checkout from 3 to 4

Original-patch-by: dependabot[bot] <[email protected]>
Signed-off-by: Johannes Schindelin <[email protected]>

Author: dependabot[bot]

.github/workflows/cygwin.yml

@@ -18,7 +18,7 @@ jobs:
       HAS_SSH_KEY: ${{ secrets.SSH_KEY != '' }}
 
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
 
     # install build tools
     - name: Install build tools
@@ -105,7 +105,7 @@ jobs:
       run: |
         icacls . /inheritance:r
         icacls . /grant Administrators:F
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
 
     # install cygwin and build tools
     - name: Install Cygwin