chore(cleanup): Remove show_cash_in_token_filters feature gate

[finnian0826]

Description

Confirmed with product that we should remove

Test plan

CI

Related issues

• Part of ACT-1443

Backwards compatibility

Yes

Network scalability

If a new NetworkId and/or Network are added in the future, the changes in this PR will:

• N/A

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.95%. Comparing base (4c5db02) to head (cb8118a).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6343      +/-   ##
==========================================
- Coverage   88.95%   88.95%   -0.01%     
==========================================
  Files         737      737              
  Lines       31445    31437       -8     
  Branches     5833     5829       -4     
==========================================
- Hits        27973    27965       -8     
  Misses       3274     3274              
  Partials      198      198              

Files with missing lines	Coverage Δ
.../fiatExchanges/FiatExchangeCurrencyBottomSheet.tsx	93.44% <100.00%> (-0.21%)	⬇️
src/statsig/types.ts	100.00% <ø> (ø)

... and 1 file with indirect coverage changes

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