Remove redundant type argument

Author: DZakh

jscomp/test/variantsMatching.gen.tsx

@@ -21,4 +21,4 @@ export type MyNullable_t<a> = null | undefined | a;
 export type MyNullableExtended_t<a> = null | undefined | "WhyNotAnotherOne" | a;
 
 // tslint:disable-next-line:interface-over-type-literal
-export type UntaggedWithBool_t<a> = string | number | boolean | string;
+export type UntaggedWithBool_t = string | number | boolean | string;

jscomp/test/variantsMatching.res

@@ -275,7 +275,7 @@ module CustomTagNotInline = {
 
 module UntaggedWithBool = {
   @unboxed @genType
-  type t<'a> = String(string) | Float(float) | Bool(bool) | Object({name: string})
+  type t = String(string) | Float(float) | Bool(bool) | Object({name: string})
 
   let classify = x =>
     switch x {