mac-vth264: Fix encoder list leak

Instruments claims there are still more around here, but they look
internal with my limited Mac knowledge.

plugins/mac-vth264/encoder.c

@@ -965,6 +965,8 @@ void encoder_list_create()
 		da_push_back(vt_encoders, &enc);
 #undef VT_DICTSTR
 	}
+
+	CFRelease(encoder_list);
 }
 
 void encoder_list_destroy()