Fix duplicate Doxygen \defgroup id for uxTaskBasePriorityGet (#1426)

uxTaskBasePriorityGet reused the \defgroup id 'uxTaskPriorityGet'
already defined by uxTaskPriorityGet, only with a different title.
Doxygen reported:

  task.h: warning: group uxTaskPriorityGet: ignoring title
  "uxTaskBasePriorityGet" that does not match old title
  "uxTaskPriorityGet"

Give uxTaskBasePriorityGet its own group id so both functions are
documented correctly.

include/task.h

diff --git a/include/task.h b/include/task.h
index 2a19fa7..2add58b 100644
--- a/include/task.h
+++ b/include/task.h
@@ -1050,7 +1050,7 @@
  *
  * @return The base priority of xTask.
  *
- * \defgroup uxTaskPriorityGet uxTaskBasePriorityGet
+ * \defgroup uxTaskBasePriorityGet uxTaskBasePriorityGet
  * \ingroup TaskCtrl
  */
 UBaseType_t uxTaskBasePriorityGet( const TaskHandle_t xTask ) PRIVILEGED_FUNCTION;