chore(docs): Update docs to suggest using preventOverflow

Alternatively, we can also set preventOverflow to true by default if left or right are used, but it sounds like the team wants to avoid setting defaults like that.

Author: rebeccaalpert

packages/react-core/src/helpers/Popper/Popper.tsx

@@ -51,7 +51,7 @@ export const getOpacityTransition = (animationDuration: number) =>
 export interface PopperOptions {
   /** popper direction */
   direction?: 'up' | 'down';
-  /** popper position */
+  /** Horizontal position of the popper. Use the additional prop preventOverflow if seeing clipping. */
   position?: 'right' | 'left' | 'center' | 'start' | 'end';
   /** Instead of direction and position can set the placement of the popper */
   placement?: Placement;