Disable WeakRef tests in test262.properties

WeakRef implementation is in a separate PR and these tests should not be enabled in the Math.sumPrecise branch

Author: anivar

tests/testsrc/test262.properties

@@ -3007,7 +3007,7 @@ built-ins/WeakMap 40/141 (28.37%)
     prototype/getOrInsert 17/17 (100.0%)
     proto-from-ctor-realm.js
 
-built-ins/WeakRef 29/29 (100.0%)
+~built-ins/WeakRef
 
 built-ins/WeakSet 1/85 (1.18%)
     proto-from-ctor-realm.js