runtime(doc): mention alternative check for vim9script

Vim9 syntax changed before Vim 9 leading to errors thrown if checked for
availability of Vim9script in Vim Version 8.2 such as

This check seems to work as well and throws less errors on Vim 8.2 such
as on Ubuntu 22.04

closes: #16783

Signed-off-by: Konfekt <Konfekt@users.noreply.github.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/vim9.txt b/runtime/doc/vim9.txt
index 5ea4ebe..3addea8 100644
--- a/runtime/doc/vim9.txt
+++ b/runtime/doc/vim9.txt
@@ -1,4 +1,4 @@
-*vim9.txt*	For Vim version 9.1.  Last change: 2025 Jan 21
+*vim9.txt*	For Vim version 9.1.  Last change: 2025 Mar 05
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -1921,6 +1921,10 @@
 This allows for writing a script that takes advantage of the Vim9 script
 syntax if possible, but will also work on a Vim version without it.
 
+Note that Vim9 syntax changed before Vim 9 so that scripts using the current
+syntax (such as "import from" instead of "import") might throw errors.
+To prevent these, a safer check could be for |v:version| >= 900 instead.
+
 This can only work in two ways:
 1. The "if" statement evaluates to false, the commands up to `endif` are
    skipped and `vim9script` is then the first command actually executed.
@@ -2435,4 +2439,4 @@
 
 
 
- vim:tw=78:ts=8:noet:ft=help:norl:
+ vim:tw=78:ts=8:noet:ft=help:norl:nofen: