runtime(doc): Capitalise the mnemonic "Zero" for the 'z' flag of search()

closes: #16384

Signed-off-by: Doug Kearns <dougkearns@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/builtin.txt b/runtime/doc/builtin.txt
index d7ed732..1b39b1b 100644
--- a/runtime/doc/builtin.txt
+++ b/runtime/doc/builtin.txt
@@ -1,4 +1,4 @@
-*builtin.txt*	For Vim version 9.1.  Last change: 2025 Jan 02
+*builtin.txt*	For Vim version 9.1.  Last change: 2025 Jan 05
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -9038,7 +9038,7 @@
 		's'	Set the ' mark at the previous location of the cursor
 		'w'	Wrap around the end of the file
 		'W'	don't Wrap around the end of the file
-		'z'	start searching at the cursor column instead of zero
+		'z'	start searching at the cursor column instead of Zero
 		If neither 'w' or 'W' is given, the 'wrapscan' option applies.
 
 		If the 's' flag is supplied, the ' mark is set, only if the