Removes the specified number of elements from the end of the collection.
mutating func removeLast(_ k: Int)
The number of elements to remove from the collection.
kmust be greater than or equal to zero and must not exceed the number of elements in the collection.
Attempting to remove more elements than exist in the collection triggers a runtime error.
Calling this method may invalidate all saved indices of this collection. Do not rely on a previously stored index value after altering a collection with any operation that can change its length.