Upgrade GitHub Actions for Node 24 compatibility

See #32

PiperOrigin-RevId: 845386328
Change-Id: I62106e7c22ef08cd858dabde23ca2d720bfc9c3c

Author: rjogrady

.github/workflows/ci.yaml

@@ -31,7 +31,7 @@ jobs:
         uses: actions/setup-python@v5
         with:
           python-version: "3.12"
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0
 

.github/workflows/update.yml

@@ -11,7 +11,7 @@ jobs:
       contents: write
     steps:
       # Update checkout version and add fetch-depth
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0