chore(ui-ux): remove bittrex from exchange list

[fullstackninja864]

What this PR does / why we need it:

Which issue(s) does this PR fixes?:

Fixes #

Additional comments?:

Developer Checklist:

• [ ] Read your code changes at least once
• [ ] Tested on iOS/Android device (e.g, No crashes, library supported etc.)
• [ ] No console errors on web
• [ ] Tested on Light mode and Dark mode*
• [ ] Your UI implementation visually matched the rendered design*
• [ ] Unit tests*
• [ ] Added e2e tests*
• [ ] Added translations*

[github-actions[bot]]

Missing Translations Report

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[github-actions[bot]]

Build preview for DeFiChain Wallet is ready!

Built with commit 4d06945efafa98a61f249b3d223ab56777e5383f

https://expo.io/@defichain/wallet?release-channel=pr-preview-4148

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (e0d2511) 53.70% compared to head (c2a3d41) 61.52%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #4148 +/- ## ========================================== + Coverage 53.70% 61.52% +7.81% ========================================== Files 438 438 Lines 12445 12445 Branches 4122 4122 ========================================== + Hits 6684 7657 +973 + Misses 5680 4696 -984 - Partials 81 92 +11 ```

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