doc: Fix the Doxygen section endings

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
diff --git a/src/rate_ctr.c b/src/rate_ctr.c
index 24166b8..8a232e8 100644
--- a/src/rate_ctr.c
+++ b/src/rate_ctr.c
@@ -177,4 +177,4 @@
 	return NULL;
 }
 
-/*! }@ */
+/*! @} */