Remove HistogramEqualizationOptions.Default

[antonfirsov]

Prerequisites

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• I have verified that there are no overlapping pull-requests open
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• I have provided test coverage for my change (where applicable)

Description

We should not expose an arbitrary mutable variable like this. The common practice in the library is to use constructor to new-up instances of similar XyzOptions objects.

[antonfirsov]

Unrelated tabs -> spaces change.

[JimBobSquarePants]

Yeah, this shouldn’t exist. Good catch!

[codecov]

Codecov Report

Merging #1840 (83455e7) into master (9777a3b) will increase coverage by 0%.
The diff coverage is 0%.

@@          Coverage Diff           @@
##           master   #1840   +/-   ##
======================================
  Coverage      87%     87%           
======================================
  Files         937     937           
  Lines       48421   48420    -1     
  Branches     6054    6054           
======================================
+ Hits        42223   42255   +32     
+ Misses       5193    5160   -33     
  Partials     1005    1005           

Flag	Coverage Δ
unittests	87% <0%> (+<1%)	⬆️

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Impacted Files	Coverage Δ
...s/Normalization/HistogramEqualizationExtensions.cs	50% <0%> (ø)
...sors/Normalization/HistogramEqualizationOptions.cs	100% <ø> (+16%)	⬆️
...rc/ImageSharp/Formats/Webp/Lossless/Vp8LEncoder.cs	97% <0%> (-1%)	⬇️
.../ImageSharp/Formats/Webp/Lossless/LosslessUtils.cs	91% <0%> (+2%)	⬆️
...ageSharp/Formats/Webp/Lossless/PredictorEncoder.cs	91% <0%> (+4%)	⬆️

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