[WORKFLOW]: fix the way I called environment variables

Author: jhabaa

.github/workflows/dotnet.yml

@@ -13,7 +13,7 @@ jobs:
         runs-on: ubuntu-latest
         env:
             MONGODB_PASSWORD: ${{ secrets.MONGODB_PASSWORD }}
-            MONGODB_NAME: $MONGODB_NAME
+            MONGODB_NAME: ${{ vars.MONGODB_NAME }}
 
         steps:
         - uses: actions/checkout@v4