Fixes #23026 - UX - Multichain - Send flow - Fix tabs in popup

[darkwing]

Description

The <Tabs> component is position: sticky which is problematic. Removing that positioning for now; we can improve in the future to make the stickiness better.

Related issues

Fixes: https://github.com/MetaMask/metamask-extension/issues/23026

Manual testing steps

1. Open the new send flow in popup with 10+ contacts
2. Scroll down
3. See tabs overlap content

Screenshots/Recordings

Before

After

https://github.com/MetaMask/metamask-extension/assets/46655/4c9cdbc8-a7b5-4fa4-b831-2cba03aed56a

Pre-merge author checklist

• [ ] I’ve followed MetaMask Coding Standards.
• [ ] I've clearly explained what problem this PR is solving and how it is solved.
• [ ] I've linked related issues
• [ ] I've included manual testing steps
• [ ] I've included screenshots/recordings if applicable
• [ ] 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.
• [ ] I’ve properly set the pull request status:
  • [ ] In case it's not yet "ready for review", I've set it to "draft".
  • [ ] In case it's "ready for review", I've changed it from "draft" to "non-draft".

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.

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