fix: remove repeated account option

[gantunesr]

Description

This PR fixes an issue about the account option Add a new Bitcoin account (testnet) being repeated.

Related issues

Fixes: None

Manual testing steps

1. Enable bitcoin testnet account in the experimental setting
2. Go to the "Add account" menu

Screenshots/Recordings

Before

After

Pre-merge author checklist

• I've followed MetaMask Contributor Docs and MetaMask Extension Coding Standards.
• I've completed the PR template to the best of my ability
• I’ve included tests if applicable
• I’ve documented my code using JSDoc format if applicable
• I’ve applied the right labels on the PR (see labeling guidelines). Not required for external contributors.

Pre-merge reviewer checklist

• I've manually tested the PR (e.g. pull and build branch, run the app, test code being changed).
• I confirm that this PR addresses all acceptance criteria described in the ticket it closes and includes the necessary testing evidence such as recordings and or screenshots.

[k-g-j]

LGTM - I only see one add testnet account option now 👍

[github-actions]

CLA Signature Action: All authors have signed the CLA. You may need to manually re-run the blocking PR check if it doesn't pass in a few minutes.

[metamaskbot]

No release label on PR. Adding release label release-12.3.0 on PR, as PR was added to branch 12.3.0 when release was cut.