runtime(doc): fix claim that 'CTRL-W CTRL-C' and 'CTRL-W c' are the same

closes: #17776

Signed-off-by: Emilien Breton <bricktech2000@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

Author: Bricktech2000

runtime/doc/index.txt

@@ -1,4 +1,4 @@
-*index.txt*     For Vim version 9.1.  Last change: 2025 Jun 28
+*index.txt*     For Vim version 9.1.  Last change: 2025 Jul 17
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -530,7 +530,7 @@ tag		command		   action in op-pending and Visual mode	~
 tag		command		   action in Normal mode	~
 ------------------------------------------------------------------------------
 |CTRL-W_CTRL-B|	CTRL-W CTRL-B	   same as "CTRL-W b"
-|CTRL-W_CTRL-C|	CTRL-W CTRL-C	   same as "CTRL-W c"
+|CTRL-W_CTRL-C|	CTRL-W CTRL-C	   no-op |CTRL-W_CTRL-C|
 |CTRL-W_CTRL-D|	CTRL-W CTRL-D	   same as "CTRL-W d"
 |CTRL-W_CTRL-F|	CTRL-W CTRL-F	   same as "CTRL-W f"
 		CTRL-W CTRL-G	   same as "CTRL-W g .."