Doxygen description of stub for CFE_SB_SendMsg is not correct

[asgibson]

Describe the bug
Description on the stub for CFE_SB_SendMsg is out of date.

Expected behavior
Update description

Code snips

cFE/fsw/cfe-core/ut-stubs/ut_sb_stubs.c

Lines 453 to 462 in 8a7dc8f

	** \par Description
	** This function is used to mimic the response of the cFE SB function
	** CFE_SB_SendMsg. The user can adjust the response by setting
	** the values in the SBSendMsgRtn structure prior to this function
	** being called. If the value SBSendMsgRtn.count is greater than
	** zero then the counter is decremented; if it then equals zero the
	** return value is set to the user-defined value SBSendMsgRtn.value.
	** CFE_SUCCESS is returned otherwise. Only EVS and TIME messages are
	** handled directly by this function; other messages are passed to the
	** unit test function, UT_ProcessSBMsg, for any further action.

Reporter Info
Alan Gibson NASA GSFC/587

[skliper]

Stub deprecated in #1015, CFE_SB_TransmitMsg stub is documented correctly.