Update references

[JimBobSquarePants]

Prerequisites

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

Description

Upstream ImageSharp version contains breaking runtime changes due to API updates. We need to update and rebuild.

[codecov]

Codecov Report

Merging #186 (8f974dd) into master (0e586c3) will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff          @@
##           master   #186   +/-   ##
=====================================
  Coverage      70%    70%           
=====================================
  Files          87     87           
  Lines        5116   5116           
  Branches     1062   1062           
=====================================
  Hits         3593   3593           
  Misses       1308   1308           
  Partials      215    215           

Flag	Coverage Δ
unittests	70% <100%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/ImageSharp.Drawing/Processing/GradientBrush.cs	85% <100%> (ø)
src/ImageSharp.Drawing/Processing/ImageBrush.cs	87% <100%> (ø)
...ImageSharp.Drawing/Processing/PathGradientBrush.cs	87% <100%> (ø)
src/ImageSharp.Drawing/Processing/PatternBrush.cs	83% <100%> (ø)
...ng/Processors/Drawing/FillPathProcessor{TPixel}.cs	100% <100%> (ø)
...essing/Processors/Drawing/FillProcessor{TPixel}.cs	100% <100%> (ø)
...ssing/Processors/Text/DrawTextProcessor{TPixel}.cs	96% <100%> (ø)
src/ImageSharp.Drawing/Processing/RecolorBrush.cs	96% <100%> (ø)
src/ImageSharp.Drawing/Processing/SolidBrush.cs	94% <100%> (ø)

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