UI: Change Simple Output NVENC default preset to P5

To avoid the user having lookahead enabled with no way to disable it,
change the Simple Output Mode NVENC Preset from P6 to P5.

Follow up to 8806738a04a651b147aff68fbddfb688c8d179db.

UI/window-basic-main.cpp

@@ -1399,7 +1399,7 @@ bool OBSBasic::InitBasicConfigDefaults()
 	config_set_default_string(basicConfig, "SimpleOutput", "Preset",
 				  "veryfast");
 	config_set_default_string(basicConfig, "SimpleOutput", "NVENCPreset2",
-				  "p6");
+				  "p5");
 	config_set_default_string(basicConfig, "SimpleOutput", "RecQuality",
 				  "Stream");
 	config_set_default_bool(basicConfig, "SimpleOutput", "RecRB", false);