Bump mini-css-extract-plugin from 1.2.0 to 1.2.1 (#15077)

Bumps [mini-css-extract-plugin](https://github.com/webpack-contrib/mini-css-extract-plugin) from 1.2.0 to 1.2.1.
- [Release notes](https://github.com/webpack-contrib/mini-css-extract-plugin/releases)
- [Changelog](https://github.com/webpack-contrib/mini-css-extract-plugin/blob/master/CHANGELOG.md)
- [Commits](https://github.com/webpack-contrib/mini-css-extract-plugin/compare/v1.2.0...v1.2.1)

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

package.json

@@ -110,7 +110,7 @@
     "lodash": "^4.17.19",
     "mark-loader": "^0.1.6",
     "marky": "^1.2.1",
-    "mini-css-extract-plugin": "^1.2.0",
+    "mini-css-extract-plugin": "^1.2.1",
     "mkdirp": "^1.0.4",
     "npmlog": "^4.1.2",
     "object-assign": "^4.1.1",