fix: correctly lauch devextreme build in demos_visual_tests

Author: chaosmirage

.github/workflows/demos_visual_tests.yml

@@ -144,7 +144,7 @@ jobs:
         shell: bash
         run: |
           pnpx nx build devextreme-scss
-          pnpx nx build devextreme
+          pnpx nx build devextreme -c testing
 
       - name: DevExtreme - Build-all
         if: needs.determine-framework-tests-scope.outputs.framework-tests-scope != 'none'