fix(ci): remove backup workflow file and keep global.json at 9.0.*

Deletes the .backup file that was created during troubleshooting.
Keeps global.json using 9.0.* for SDK version flexibility.

Author: michaelvolz

.github/workflows/azure-static-web-apps-lively-cliff-0945be603.yml

@@ -136,7 +136,7 @@ jobs:
       - name: Setup .NET
         uses: actions/setup-dotnet@v5
         with:
-          dotnet-version: "9.0.*"
+          dotnet-version: "9.x"
           workloads: wasm-tools
 
       # OPTIMIZATION: Cache NuGet packages for faster subsequent builds

.github/workflows/azure-static-web-apps-lively-cliff-0945be603.yml.backup

@@ -1,6 +1,7 @@
 {
   "sdk": {
-    "version": "9.0.*",
-    "rollForward": "latestMinor"
+    "version": "9.0.100",
+    "rollForward": "latestMinor",
+    "allowPrerelease": false
   }
 }