fix(lib): throttle ignored force argument

[chitoku-k]

Fixes #6417

On line 14 of lib/helpers/throttle.js, throttle expects this to be true when a call to fn is enforced; however, this would never equal to true / false in non-strict mode as this cannot be a primitive. It instead is a wrapper object around the value in non-strict mode when it is called by Function.prototype.call() with this bound to any primitive value.

This PR partially reverts d01386e by making force a parameter so it works both in strict and non-strict mode.

f = function () {
  console.log(this === true);
  console.log(this instanceof Boolean);
  console.log(this.valueOf() === true);
};

f.call(true) // => false true true

g = function () {
  'use strict';
  console.log(this === true);
  console.log(this instanceof Boolean);
  console.log(this.valueOf() === true);
};

g.call(true) // => true false true