[skip ci] fix GMP entry

Author: Girgias

UPGRADING

@@ -1005,8 +1005,9 @@ PHP 8.4 UPGRADE NOTES
     deprecated in libcurl 7.11.1 and removed in 7.62.0.
 
 - GMP:
-  . Casting a GMP object to bool changed so that 0 becomes false and everything else
-    becomes true.
+  . Casting a GMP object to bool is now possible instead of emitting a
+    E_RECOVERABLE_ERROR. The casting behaviour is overloaded such that a GMP
+    object representing the value 0 is cast to false.
     RFC: https://wiki.php.net/rfc/fix_up_bcmath_number_class
 
 - Intl: