office-ui-fabric-react v6.164.0

Minor changes

• Stack: Adding margin as a token of StackItem and childrenGap as a token of Stack and updating examples accordingly. (commit by khmakoto, pr #8247)
• Separator: promote to OUFR (commit by natalieethell, pr #8519)

Patches

• ContextualMenu: Remove extra role=menu (commit by joschect, pr #8535)
• MaskedTextField: fixes the state update when the value it's controlled by the host app. (commit by Vitalius1, pr #8529)
• More TextField example updates (commit by ecraig12345, pr #8540)