VGMStream: Fix fade time configuration

Fade time was reading from some completely wrong
configuration field name, so fades weren't working.

Plugins/vgmstream/vgmstream/VGMDecoder.m

@@ -243,7 +243,7 @@ - (BOOL)open:(id<CogSource>)s {
 		loopCount = 10;
 	}
 
-	fadeTime = [[[[NSUserDefaultsController sharedUserDefaultsController] defaults] valueForKey:@"synthDefaultFadeTime"] doubleValue];
+	fadeTime = [[[[NSUserDefaultsController sharedUserDefaultsController] defaults] valueForKey:@"synthDefaultFadeSeconds"] doubleValue];
 	if(fadeTime < 0.0) {
 		fadeTime = 0.0;
 	}