Clarified ambiguous test wording for arrays.js remove and removeWithoutCopy functions on whether to remove a single instance or all instances of a given value

Before, wording was unclear in arrays.js tests for remove and
removeWithoutCopy that the intent is not to remove a specific value, or
a single instance of an value, but rather all instances of a value from
an array.

Update ambiguous text for expected behavior in test wording for
arrays.js