Fix performance issue in redundancy removal

[blegat]

For the example of #279, this PR gives almost a 10x speedup!
Before:

0.159333 seconds (63.51 k allocations: 8.252 MiB)

After:

0.018471 seconds (10.34 k allocations: 909.406 KiB)

Closes #279

[codecov]

Codecov Report

Merging #280 (704e4eb) into master (0288f27) will increase coverage by 0.20%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #280      +/-   ##
==========================================
+ Coverage   88.14%   88.34%   +0.20%     
==========================================
  Files          37       37              
  Lines        2894     2901       +7     
==========================================
+ Hits         2551     2563      +12     
+ Misses        343      338       -5     

Impacted Files	Coverage Δ
src/opt.jl	89.53% <100.00%> (+5.81%)	⬆️
src/redundancy.jl	91.24% <100.00%> (+0.29%)	⬆️

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