doc: Fix the Doxygen section endings

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
diff --git a/src/timer.c b/src/timer.c
index 79d4ad6..cca2a23 100644
--- a/src/timer.c
+++ b/src/timer.c
@@ -233,4 +233,4 @@
 	return i;
 }
 
-/*! }@ */
+/*! @} */