fe: remove mdast-util-to-hast override

Our @redpanda-data/ui package uses v12 while the
rest of our stack uses v13. In v13 there was a
breaking change:

syntax-tree/mdast-util-to-hast@40e1d29

That makes our e2e tests fail. Removing the
override for now, we should take this bump
in the upstream dependency instead.

Author: r-vasquez

frontend/bun.lock

@@ -52,7 +52,6 @@
     "@hono/node-server": "^1.19.10",
     "lodash": "^4.17.23",
     "lodash-es": "^4.17.23",
-    "mdast-util-to-hast": "^13.2.1",
     "qs": "^6.14.2"
   },
   "dependencies": {