Bump mobx from 6.5.0 to 6.6.0 (#5570)

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Sebastian Malton <sebastian@malton.name>

package.json

@@ -242,7 +242,7 @@
     "mac-ca": "^1.0.6",
     "marked": "^4.0.17",
     "md5-file": "^5.0.0",
-    "mobx": "^6.5.0",
+    "mobx": "^6.6.0",
     "mobx-observable-history": "^2.0.3",
     "mobx-react": "^7.5.0",
     "mobx-utils": "^6.0.4",