Update docker image building workflow

Author: hustcer

.github/workflows/nightly-alpine.yaml

@@ -20,7 +20,7 @@ jobs:
       - name: Checkout Code
         uses: actions/checkout@v4
         with:
-          ref: nightly
+          ref: main
 
       - name: Set up Nushell
         uses: hustcer/setup-nu@v3

.github/workflows/pre-release.yml

@@ -3,7 +3,7 @@ name: Pre Release
 on:
   push:
     branches:
-      - nightly   # Just for test purpose only with the nightly repo
+      - nightly0    # Just for test purpose only with the nightly repo
   # This schedule will run only from the default branch
   schedule:
     - cron: '30 1 * * *' # run at 00:15 AM UTC