office-ui-fabric-react v7.120.0

Minor changes

• PivotItem: Fixing typing error in headerButtonProps. (PR #13550 by khmakoto)

Patches

• Update Details and Grouped list chevron to rotate in the correct direction for RTL. (PR #13514 by bcoard)
• Combobox: Fix openOnKeyboard prop to work as expected (PR #13520 by joschect)
• Fix some unnecessary DetailsList styles (PR #13540 by phkuo)