Update Multiscreen Blank checkver regex

This commit fixes a small bug with the regular expression used to check
the version for Multiscreen Blank. It previously had an unescaped
period, allowing for any value instead of actual periods.

bucket/multiscreenblank.json

 	],
 	"checkver": {
 		"url": "http://dl.nookkin.com/products/multiscreenblank/latest/",
-		"regex": "MultiscreenBlank([\\d.]+)\\.zip"
+		"regex": "MultiscreenBlank([\\d\\.]+)\\.zip"
 	}
 }