chore: update template framework dropdown

Author: andrewbabbittdev

src/BlazorDesktop.Templates/content/BlazorDesktop-CSharp/.template.config/template.json

@@ -73,12 +73,12 @@
       "datatype": "choice",
       "choices": [
         {
-          "choice": "net8.0",
-          "description": "Target net8.0"
+          "choice": "net9.0",
+          "description": "Target net9.0"
         }
       ],
-      "replaces": "net8.0",
-      "defaultValue": "net8.0"
+      "replaces": "net9.0",
+      "defaultValue": "net9.0"
     },
     "HostIdentifier": {
       "type": "bind",