Clear ps display of startup process at the end of recovery

If the ps display is not cleared at this point, the process could
continue displaying "recovering NNN" even if handling end-of-recovery
steps.  df9274a has tackled that by providing some information with the
end-of-recovery checkpoint but 7ff23c6 has nullified the effect of the
first commit.

Per a suggestion from Justin, just clear the ps display when we are done
with recovery, so as no incorrect information is displayed.  This may
get extended in the future, but for now restore the pre-7ff23c6
behavior.

Author: Justin Prysby
Discussion: https://postgr.es/m/20220913223954.GU31833@telsasoft.com
Backpatch-through: 15

src/backend/access/transam/xlog.c

@@ -5312,6 +5312,12 @@ StartupXLOG(void)
 	abortedRecPtr = endOfRecoveryInfo->abortedRecPtr;
 	missingContrecPtr = endOfRecoveryInfo->missingContrecPtr;
 
+	/*
+	 * Reset ps status display, so as no information related to recovery
+	 * shows up.
+	 */
+	set_ps_display("");
+
 	/*
 	 * When recovering from a backup (we are in recovery, and archive recovery
 	 * was requested), complain if we did not roll forward far enough to reach