Merge "[Thread] remove thread_user_restriction_enabled" into main

thread/flags/thread_base.aconfig

@@ -6,10 +6,3 @@ flag {
     description: "Controls whether the Android Thread feature is enabled"
     bug: "301473012"
 }
-
-flag {
-    name: "thread_user_restriction_enabled"
-    namespace: "thread_network"
-    description: "Controls whether user restriction on thread networks is enabled"
-    bug: "307679182"
-}