update nightly build schedule

.github/workflows/buildx.yml

@@ -57,7 +57,7 @@ jobs:
 
       # https://github.com/actions/checkout
     - name: Checkout
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
 
     - name: Docker Buildx (no push)
       run: |

.github/workflows/trigger-nightly.yml

@@ -3,7 +3,7 @@ name: Trigger nightly build
 on:
   schedule:
     # * is a special character in YAML, so you have to quote this string
-    - cron:  '00 20 * * *'
+    - cron:  '00 15 * * *'
   workflow_dispatch:
 
 jobs: