Restore allowPrerelease=false and rollForward=latestFeature in global.json

Was removed in 725b6b2 but will be useful when the next versions of the .NET 8 SDK will be published.

Author: 0xced

global.json

@@ -1,5 +1,7 @@
 {
   "sdk": {
-    "version": "8.0.100"
+    "version": "8.0.100",
+    "allowPrerelease": false,
+    "rollForward": "latestFeature"
   }
 }