TS version back to 2.3

I tested with 3.3 and thought the comment referred to the latest compatible version. But yes, 3.3 is not a requirement.

types/mongo-sanitize/index.d.ts

@@ -2,7 +2,7 @@
 // Project: https://github.com/vkarpov15/mongo-sanitize
 // Definitions by: Cedric Cazin <https://github.com/CedricCazin>, Olga Isakova <https://github.com/penumbra1>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
-// TypeScript Version: 3.3
+// TypeScript Version: 2.3
 
 declare function sanitize<T>(v: T): T;