Stop strict typechecking for Symbol.iterator

`typeof Symbol.iterator === 'symbol'` is not polyfillable

Author: smikitky

multi-integer-range.ts

@@ -498,7 +498,7 @@ export default MultiRange;
 
 // Set ES6 iterator, if Symbol.iterator is defined
 /* istanbul ignore else */
-if (typeof Symbol === 'function' && typeof Symbol.iterator === 'symbol') {
+if (typeof Symbol === 'function' && 'iterator' in Symbol) {
 	MultiRange.prototype[Symbol.iterator] = MultiRange.prototype.getIterator;
 }