Remove unused helper mixins

[dreikanter]

Changes:

• Remove unused helper-module mixins from the feed filter and sort dropdown components.

Why:

Both components already access view helpers through the component helper proxy.

References:

• Related issue: Review the code structure #1010 (F-063)

Checks:

• Executable behavior is unchanged.
• GitHub Actions will verify the branch.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.55%. Comparing base (ce0547a) to head (97f3f03).
⚠️ Report is 7 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1084      +/-   ##
==========================================
- Coverage   97.55%   97.55%   -0.01%     
==========================================
  Files         355      355              
  Lines        8358     8356       -2     
==========================================
- Hits         8154     8152       -2     
  Misses        204      204              

Files with missing lines	Coverage Δ
app/components/feed_filter_dropdown_component.rb	100.00% <ø> (ø)
app/components/sort_dropdown_component.rb	100.00% <ø> (ø)

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