runtime(doc): Correct allowed flags after :substitute repeat

closes: #17391

Signed-off-by: Doug Kearns <dougkearns@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/change.txt b/runtime/doc/change.txt
index 24137c7..6bf9e2c 100644
--- a/runtime/doc/change.txt
+++ b/runtime/doc/change.txt
@@ -1,4 +1,4 @@
-*change.txt*    For Vim version 9.1.  Last change: 2025 Apr 03
+*change.txt*    For Vim version 9.1.  Last change: 2025 May 28
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -664,8 +664,9 @@
 			Repeat last :substitute with same search pattern and
 			substitute string, but without the same flags.  You
 			may add [flags], see |:s_flags|.
-			Note that after `:substitute` the '&' flag can't be
-			used, it's recognized as a pattern separator.
+			Note that after `:substitute` the '&' and '#' flags
+			can't be used, they're recognized as a pattern
+			separator.
 			The space between `:substitute` and the 'c', 'g',
 			'i', 'I' and 'r' flags isn't required, but in scripts
 			it's a good idea to keep it to avoid confusion.