help: mark unused parameter in git_unknown_cmd_config()

The extra callback parameter became unused in 0918d08 (help.c: fix
autocorrect in work tree for bare repository, 2022-10-29), but we can't
get rid of it because we must conform to the config callback interface.

Signed-off-by: Jeff King <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: peff

help.c

@@ -540,7 +540,8 @@ static struct cmdnames aliases;
 #define AUTOCORRECT_NEVER (-2)
 #define AUTOCORRECT_IMMEDIATELY (-1)
 
-static int git_unknown_cmd_config(const char *var, const char *value, void *cb)
+static int git_unknown_cmd_config(const char *var, const char *value,
+				  void *cb UNUSED)
 {
 	const char *p;