Bump mobx from 6.7.0 to 6.8.0 (#7170)

Bumps [mobx](https://github.com/mobxjs/mobx) from 6.7.0 to 6.8.0.
- [Release notes](https://github.com/mobxjs/mobx/releases)
- [Commits](https://github.com/mobxjs/mobx/commits)

---
updated-dependencies:
- dependency-name: mobx
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

packages/core/package.json

@@ -163,7 +163,7 @@
     "lodash": "^4.17.15",
     "marked": "^4.2.12",
     "md5-file": "^5.0.0",
-    "mobx": "^6.7.0",
+    "mobx": "^6.8.0",
     "mobx-observable-history": "^2.0.3",
     "mobx-react": "^7.6.0",
     "mobx-utils": "^6.0.4",