Bump @storybook/addon-storysource from 6.4.0 to 6.4.7 (#986)

Bumps [@storybook/addon-storysource](https://github.com/storybookjs/storybook/tree/HEAD/addons/storysource) from 6.4.0 to 6.4.7.
- [Release notes](https://github.com/storybookjs/storybook/releases)
- [Changelog](https://github.com/storybookjs/storybook/blob/v6.4.7/CHANGELOG.md)
- [Commits](https://github.com/storybookjs/storybook/commits/v6.4.7/addons/storysource)

---
updated-dependencies:
- dependency-name: "@storybook/addon-storysource"
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

package.json

@@ -30,7 +30,7 @@
     "@rollup/plugin-replace": "^3.0.0",
     "@storybook/addon-knobs": "6.3.1",
     "@storybook/addon-storyshots": "^6.3.12",
-    "@storybook/addon-storysource": "6.4.0",
+    "@storybook/addon-storysource": "6.4.7",
     "@storybook/svelte": "6.1.21",
     "@testing-library/svelte": "^3.0.3",
     "autoprefixer": "^10.4.0",