libobs: Fix PulseAudio monitoring when device is set to default

When the monitoring device is set to default, this bit of code was
appending the no-longer-needed ".monitor" to the device name.

Fixes #8877

libobs/audio-monitoring/pulse/pulseaudio-wrapper.c

@@ -54,7 +54,6 @@ void get_default_id(char **id)
 	} else {
 		*id = bzalloc(strlen(pdo->default_sink_name) + 9);
 		strcat(*id, pdo->default_sink_name);
-		strcat(*id, ".monitor");
 		bfree(pdo->default_sink_name);
 	}