chore(deps): update storybook monorepo to v6.1.5

[renovate[bot]]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
@storybook/addon-backgrounds	6.1.4 -> 6.1.5
@storybook/addon-docs	6.1.4 -> 6.1.5
@storybook/addon-essentials	6.1.4 -> 6.1.5
@storybook/addon-knobs	6.1.4 -> 6.1.5
@storybook/addon-storysource	6.1.4 -> 6.1.5
@storybook/addon-toolbars	6.1.4 -> 6.1.5
@storybook/addon-viewport	6.1.4 -> 6.1.5
@storybook/addons	6.1.4 -> 6.1.5
@storybook/node-logger	6.1.4 -> 6.1.5
@storybook/preact	6.1.4 -> 6.1.5
@storybook/theming	6.1.4 -> 6.1.5
@storybook/web-components	6.1.4 -> 6.1.5

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Release Notes

storybookjs/storybook

### [`v6.1.5`](https://togithub.com/storybookjs/storybook/compare/v6.1.4...v6.1.5) [Compare Source](https://togithub.com/storybookjs/storybook/compare/v6.1.4...v6.1.5)

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