Fix up typo in Blazor Server launchSettings.json (#31580)

Author: pranavkm

src/ProjectTemplates/Web.ProjectTemplates/content/BlazorServerWeb-CSharp/Properties/launchSettings.json

@@ -37,6 +37,6 @@
       "environmentVariables": {
         "ASPNETCORE_ENVIRONMENT": "Development"
       }
-    },
+    }
   }
 }