Minor bugs in BigInt tests

[jakobkummerow]

CC @rwaldron @leobalter @gsathya

I've found two minor issues with BigInt tests:

built-ins/BigInt/prototype/Symbol.toStringTag.js:
"verifyProperty" is destructive unless {restore: true} is passed. This makes the subsequent assert fail.
Fix:

--- a/test/built-ins/BigInt/prototype/Symbol.toStringTag.js
+++ b/test/built-ins/BigInt/prototype/Symbol.toStringTag.js
@@ -19,7 +19,7 @@ verifyProperty(BigInt.prototype, Symbol.toStringTag, {
   writable: false,
   enumerable: false,
   configurable: true
-});
+}, {restore: true});
 
 assert.sameValue(Object.prototype.toString.call(3n), "[object BigInt]");
 assert.sameValue(Object.prototype.toString.call(Object(3n)), "[object BigInt]");

built-ins/TypedArrays/ctors-bigint/typedarray-arg/typedarray-arg-other-ctor-returns-new-typedarray.js:
The inputs must have length 7 in order for the newly constructed arrays to have length 7 as well.
Fix:

--- a/test/built-ins/TypedArrays/ctors-bigint/typedarray-arg/typedarray-arg-other-ctor-returns-new-typedarray.js
+++ b/test/built-ins/TypedArrays/ctors-bigint/typedarray-arg/typedarray-arg-other-ctor-returns-new-typedarray.js
@@ -14,8 +14,8 @@ includes: [testBigIntTypedArray.js]
 features: [BigInt, TypedArray]
 ---*/
 
-var sample1 = new BigInt64Array();
-var sample2 = new BigUint64Array();
+var sample1 = new BigInt64Array(7);
+var sample2 = new BigUint64Array(7);
 
 testWithBigIntTypedArrayConstructors(function(TA) {
   var sample = TA === BigInt64Array ? sample2 : sample1;

[littledan]

cc @cxielarko

[cxielarko]

These changes LGTM! (the second test fails in spidermonkey too; the first passes but probably shouldn't)