Fix misleading phrase "arrays of lists" in stack implementation description

[danmondra]

This PR fixes a minor but potentially confusing phrase in the explanation of stack implementations. This small change is intended to provide clarity to readers.

The original sentence:

"We can make use of linked lists or arrays of lists."

has been updated to:

"Stacks can be implemented using either arrays or linked lists."

Reason for Change

The phrase "arrays of lists" is misleading when discussing stack implementations. It may suggest a 2D structure or a collection of lists, which is not relevant for implementing a basic stack. Stacks are most commonly implemented using either:

1. Arrays (for static or dynamic sizing)
2. Linked lists (for dynamic memory usage)