Add scrollbar to the missing content list when using "Redistribute All Failed Content Transfers" on distribution points.

When using RCT's "Redistribute All Failed Content Transfers" feature, all failed packages on that particular Distribution Point are listed in a pop-up window, prompting the user to continue with re-distribution. If the list is big enough, and in rare cases it can be, the window will outsize the screen, making it impossible to navigate to the accept button or even entirely review the list. Placing this list in a scrollable pane will greatly improve this experience and will make the window far more helpful.