Update dependencies

[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

Updated all dependent packages to latest version.

[codecov]

Codecov Report

Merging #600 into master will decrease coverage by 0.07%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #600      +/-   ##
==========================================
- Coverage   88.78%   88.71%   -0.08%     
==========================================
  Files         854      854              
  Lines       36207    36207              
  Branches     2624     2624              
==========================================
- Hits        32147    32121      -26     
- Misses       3280     3284       +4     
- Partials      780      802      +22

Impacted Files	Coverage Δ
...Processing/Transforms/ProjectiveTransformHelper.cs	86.11% <0%> (-11.12%)	⬇️
src/ImageSharp/Common/Helpers/ImageMaths.cs	77.41% <0%> (-6.46%)	⬇️
...sing/Dithering/ErrorDiffusion/ErrorDiffuserBase.cs	93.1% <0%> (-3.45%)	⬇️
...Formats/Jpeg/GolangPort/Components/Decoder/Bits.cs	69.69% <0%> (-3.04%)	⬇️
...sts/Formats/Jpg/DoubleBufferedStreamReaderTests.cs	97.33% <0%> (-2.67%)	⬇️
.../ImageSharp.Tests/TestUtilities/TestEnvironment.cs	82.5% <0%> (-2.5%)	⬇️
...c/ImageSharp/Formats/Png/Zlib/ZlibDeflateStream.cs	61.4% <0%> (-1.76%)	⬇️
...Tests/TestUtilities/ImageProviders/FileProvider.cs	63.33% <0%> (-1.67%)	⬇️
...TestUtilities/Attributes/ImageDataAttributeBase.cs	83.33% <0%> (-1.67%)	⬇️
tests/ImageSharp.Tests/TestUtilities/TestUtils.cs	81.01% <0%> (-1.27%)	⬇️
... and 15 more

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