docs: update Claude's guide (coder#18523)

## PR Summary
Commit 5df70a6 added by mistake the the
following old line to `CLAUDE.md`:
```
For building Frontend refer to [this document](docs/contributing/frontend.md)
```
This PR removes it.

Signed-off-by: Emmanuel Ferdman <emmanuelferdman@gmail.com>

Author: emmanuel-ferdman