debug: symtab: move to os_services doxygen group

Instead of being a top-level group.

Signed-off-by: Gerard Marull-Paretas <[email protected]>

Author: gmarull

include/zephyr/debug/symtab.h

@@ -15,6 +15,7 @@ extern "C" {
 
 /**
  * @defgroup symtab_apis Symbol Table API
+ * @ingroup os_services
  * @{
  */