Bump @storybook/manager-webpack5 from 6.3.10 to 6.4.0 (#7392)

Bumps [@storybook/manager-webpack5](https://github.com/storybookjs/storybook/tree/HEAD/lib/core) from 6.3.10 to 6.4.0.
- [Release notes](https://github.com/storybookjs/storybook/releases)
- [Changelog](https://github.com/storybookjs/storybook/blob/next/CHANGELOG.md)
- [Commits](https://github.com/storybookjs/storybook/commits/v6.4.0/lib/core)

---
updated-dependencies:
- dependency-name: "@storybook/manager-webpack5"
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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