Update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/manual-build.yml

@@ -22,7 +22,7 @@ jobs:
     permissions:
       contents: write
     steps:
-      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
         with:
           fetch-depth: 0
           persist-credentials: false

.github/workflows/sync.yml

@@ -20,7 +20,7 @@ jobs:
       contents: write
       issues: write
     steps:
-      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
         with:
           fetch-depth: 0
           persist-credentials: true # needed for git push later

.github/workflows/zizmor.yml

@@ -16,7 +16,7 @@ jobs:
       security-events: write
 
     steps:
-      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
         with:
           persist-credentials: false