Fix schema type issue in validator.ts

[jerboa88]

Argument of type 'BooleanSchema | NumberSchema | StringSchema | ObjectSchema<unknown>' is not assignable to parameter of type 'BooleanSchema & StringSchema & ObjectSchema<unknown> & NumberSchema'.
  Type 'BooleanSchema' is not assignable to type 'BooleanSchema & StringSchema & ObjectSchema<unknown> & NumberSchema'.
    Type 'BooleanSchema' is missing the following properties from type 'StringSchema': alphanum, base64, case, creditCard, and 24 more.ts(2345)