mac-capture: Remove explicit call to setBackgroundColor

This was necessary since the default background color was meant to be
clear, but wasn't set properly. The bug is fixed in macOS 13 Beta 6, so
we can remove this statement.

plugins/mac-capture/mac-screen-capture.m

@@ -456,11 +456,6 @@ static bool init_screen_stream(struct screen_capture *sc)
 			includingApplications:target_application_array
 			     exceptingWindows:[[NSArray alloc] init]];
 
-		if (@available(macOS 13.0, *))
-			[sc->stream_properties
-				setBackgroundColor:CGColorGetConstantColor(
-							   kCGColorClear)];
-
 		set_display_mode(sc, target_display);
 	} break;
 	}