[ci skip] Fix UPGRADING section

Author: nielsdos

UPGRADING

@@ -1230,8 +1230,6 @@ PHP 8.4 UPGRADE NOTES
     on supported CPUs by ~1.3x (SSE2) and 3x - 5x (SHA-NI).
 
 - MBString:
-  . The performance of strspn() and strcspn() is greatly improved.
-    They now run in linear time instead of being bounded by quadratic time.
   . mb_strcut() is much faster now for UTF-8 and UTF-16 strings.
   . Looking up mbstring encoding names is much faster now.
   . The performance of converting SJIS-win to unicode is greatly improved.
@@ -1251,5 +1249,7 @@ PHP 8.4 UPGRADE NOTES
 
 - Standard:
   . Improved the performance of strpbrk().
+  . The performance of strspn() and strcspn() is greatly improved.
+    They now run in linear time instead of being bounded by quadratic time.
   . get_browser() is much faster now, up to 1.5x - 2.5x for some test cases.