doc: Fix the Doxygen section endings

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
diff --git a/include/osmocom/core/signal.h b/include/osmocom/core/signal.h
index 07d0e6f..cd56f68 100644
--- a/include/osmocom/core/signal.h
+++ b/include/osmocom/core/signal.h
@@ -40,6 +40,6 @@
 /* Dispatch */
 void osmo_signal_dispatch(unsigned int subsys, unsigned int signal, void *signal_data);
 
-/*! }@ */
+/*! @} */
 
 #endif /* OSMO_SIGNAL_H */