inconsistent naming of QuickPickOptions and QuickPick

[dcermak]

• VSCode Version: 1.46.1
• OS Version: irrelevant

The interface QuickPickOptions has the entry canPickMany, however this field appears as canSelectMany in the actual QuickPick.

How about making the naming consistent here?

[chrmarti]

Not sure how we got there, but since this is stable API, we'll just keep it that way. Thanks.