[ci skip] fix typo in UPGRADING

Author: devnexen

UPGRADING

@@ -282,7 +282,7 @@ PHP 8.3 UPGRADE NOTES
     now returns true on success, previously null was returned.
   . IntlChar::enumCharNames is now returning a boolean.
     Previously it returned null on success and false on failure.
-  . IntlDateFormatter::construct throws an U_ILLEGALE_ARGUMENT_ERROR
+  . IntlDateFormatter::construct throws an U_ILLEGAL_ARGUMENT_ERROR
     exception when an invalid locale had been set.
 
 - MBString: