runtime(doc): mention that 'incsearch' ignores addresses and offset

closes: #18639

Signed-off-by: Christian Brabandt <cb@256bit.org>

Author: chrisbra

runtime/doc/options.txt

@@ -5124,9 +5124,10 @@ A jump table for the options with a short description can be found at |Q_op|.
 			{not available when compiled without the
 			|+extra_search| features}
 	While typing a search command, show where the pattern, as it was typed
-	so far, matches.  The matched string is highlighted.  If the pattern
-	is invalid or not found, nothing is shown.  The screen will be updated
-	often, this is only useful on fast terminals.
+	so far, matches (ignoring {offset} and {address} modifiers).  The
+	matched string is highlighted.  If the pattern is invalid or not
+	found, nothing is shown.  The screen will be updated often, this is
+	only useful on fast terminals.
 	Also applies to the pattern in commands: >
 		:global
 		:lvimgrep