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]

Missing Translations Report

The following translations are missing for this pull request.

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[github-actions]

Build preview for DeFiChain Wallet is ready!

Built with commit 4d06945

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

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

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

Additional details and impacted files

@@            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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