Workflow: set default shell to sh

Signed-off-by: supphakitd <67319010028@technictrang.ac.th>

.gitea/workflows/build-image.yml

@@ -5,6 +5,9 @@ on: [push]
 jobs:
   Build Docker Image:
     runs-on: ubuntu-node
+    defaults:
+      run:
+        shell: sh
     steps:
       - name: Check out repository code
         uses: actions/checkout@v4