Update UPGRADING

Author: LamentXU123

UPGRADING

@@ -47,6 +47,8 @@ PHP 8.6 UPGRADE NOTES
 - Standard:
   . Invalid mode values now throw in array_filter() instead of being silently
     defaulted to 0.
+  . Added form feed (\f) in the default trimmed characters of trim(), rtrim()
+    and ltrim().
 
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 2. New Features