chore: migrate to latest storybook 6.2.x

[Hotell]

Description

we are currently at 6.0.x

To leverage latest features that are being added to SB we wanna stay up to date.

Also being on latest will help us troubleshoot any issues we might run into (a11y/plugins/etc...)

Things to be aware while migrating:

• when migrating to 6.0.x we run into issues how SB renders stories that use deprecated storiesOf API (duplicates them), which led into vr-tests failures
  • https://github.com/microsoft/fluentui/blob/master/apps/vr-tests/src/utilities/FabricDecorator.tsx#L47-L72

Steps to verify that migration worked

• CI passes
• run yarn workspace @fluentui/react-menu storybook and check that everything works
• run yarn workspace @fluentui/react-components start and check that everything works