Remove compiler conditions

[JimBobSquarePants]

Prerequisites

• [x] I have written a descriptive pull-request title
• [x] I have verified that there are no overlapping pull-requests open
• [x] I have verified that I am following matches the existing coding patterns and practice as demonstrated in the repository. These follow strict Stylecop rules :cop:.
• [x] I have provided test coverage for my change (where applicable)

Description

Removes all outdated #if...#else conditions from the code.

[codecov[bot]]

Codecov Report

Merging #288 (b3078c1) into main (b23aa22) will increase coverage by 0%. The diff coverage is 83%.

@@         Coverage Diff          @@
##           main   #288    +/-   ##
====================================
  Coverage    80%    80%            
====================================
  Files        99     97     -2     
  Lines      5055   4875   -180     
  Branches    919    880    -39     
====================================
- Hits       4050   3925   -125     
+ Misses      807    753    -54     
+ Partials    198    197     -1     

Flag	Coverage Δ
unittests	80% <83%> (+<1%)	:arrow_up:

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Files Changed	Coverage Δ
src/ImageSharp.Drawing/Shapes/Path.cs	75% <ø> (ø)
...mageSharp.Drawing/Shapes/PolygonClipper/Clipper.cs	97% <ø> (ø)
...arp.Drawing/Shapes/PolygonClipper/ClipperOffset.cs	100% <ø> (ø)
....Drawing/Shapes/PolygonClipper/PolygonOffsetter.cs	72% <0%> (-1%)	:arrow_down:
...c/ImageSharp.Drawing/Utilities/NumericUtilities.cs	100% <ø> (ø)
...arp.Drawing/Shapes/Rasterization/ActiveEdgeList.cs	98% <100%> (ø)
...arp.Drawing/Shapes/Rasterization/PolygonScanner.cs	96% <100%> (ø)

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