doxygen: score: adjust doc in watchdog.h to doxygen guidelines

Update #3706.

cpukit/include/rtems/score/watchdog.h

@@ -37,13 +37,16 @@ extern "C" {
  *
  * @ingroup RTEMSScore
  *
+ * @brief Watchdog Handler
+ *
  * This handler encapsulates functionality related to the scheduling of
  * watchdog functions to be called at specific times in the future.
  *
  * @note This handler does not have anything to do with hardware watchdog
  *       timers.
+ *
+ * @{
  */
-/**@{*/
 
 typedef struct Watchdog_Control Watchdog_Control;
 
@@ -114,7 +117,7 @@ struct Watchdog_Control {
   uint64_t expire;
 };
 
-/**@}*/
+/** @} */
 
 #ifdef __cplusplus
 }