Documentation/CodingStyle: fix example macro parenthesis imbalance

Cc: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Fixes: f2027543 ('documentation: update CodingStyle on local variables naming in macros')
Signed-off-by: NBaruch Siach <baruch@tkos.co.il>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>

Documentation/CodingStyle

@@ -670,7 +670,7 @@ functions:
 	typeof(x) ret;			\
 	ret = calc_ret(x);		\
 	(ret);				\
-)}
+})
 
 ret is a common name for a local variable - __foo_ret is less likely
 to collide with an existing variable.