UI: Fix custom buffer size for simple output

The buffer size was being saved as 'VBufsize' while all read operations
tried to read 'Bufsize'

obs/window-basic-main-outputs.cpp

@@ -104,7 +104,7 @@ void SimpleOutput::Update()
 	int videoBitrate = config_get_uint(main->Config(), "SimpleOutput",
 			"VBitrate");
 	int videoBufsize = config_get_uint(main->Config(), "SimpleOutput",
-			"Bufsize");
+			"VBufsize");
 	int audioBitrate = config_get_uint(main->Config(), "SimpleOutput",
 			"ABitrate");
 	bool advanced = config_get_bool(main->Config(), "SimpleOutput",

obs/window-basic-settings.cpp

@@ -829,7 +829,7 @@ void OBSBasicSettings::LoadSimpleOutputSettings()
 	int videoBitrate = config_get_uint(main->Config(), "SimpleOutput",
 			"VBitrate");
 	int videoBufsize = config_get_uint(main->Config(), "SimpleOutput",
-			"Bufsize");
+			"VBufsize");
 	int audioBitrate = config_get_uint(main->Config(), "SimpleOutput",
 			"ABitrate");
 	bool reconnect = config_get_bool(main->Config(), "SimpleOutput",