Bugzilla

Let's please remove Chatbot experiments from Firefox Labs Nightly and Release 135. 

**Rationale**
- In Nightly 135, we will [flip the sidebar.revamp to true](https://bugzilla.mozilla.org/show_bug.cgi?id=1932868), and the chatbot will become available on an opt-in basis to all Nightly users (so we no longer need the checkbox). 

- In Nightly and Release 135, we would need to launch a Nimbus rollout instead of adding the experiments via a .toml file.

Let's please remove Chatbot experiments from Firefox Labs Nightly and Release 135. 

**Rationale**
- In Nightly 135, we will [flip the sidebar.revamp to true](https://bugzilla.mozilla.org/show_bug.cgi?id=1932868), and the chatbot will become available on an opt-in basis to all Nightly users (so we no longer need the checkbox). 

- In Nightly and Release 135, we would need to launch a Nimbus rollout instead of adding the experiments via a .toml file.

Let's triple-confirm the Nimbus team readiness for 135 before we start on this, though.