doc: Fix the Doxygen section endings

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
diff --git a/include/osmocom/core/msgb.h b/include/osmocom/core/msgb.h
index e465ec2..5457a07 100644
--- a/include/osmocom/core/msgb.h
+++ b/include/osmocom/core/msgb.h
@@ -365,6 +365,6 @@
 uint16_t msgb_length(const struct msgb *msg);
 void msgb_set_talloc_ctx(void *ctx);
 
-/*! }@ */
+/*! @} */
 
 #endif /* _MSGB_H */