Fixes #3976. SixLabors.ImageSharp nuget package is reporting as vulnerable

[BDisp]

Fixes

• Fixes SixLabors.ImageSharp nuget package is reporting as vulnerable #3976

Proposed Changes/Todos

• Updated to version 3.1.7

Pull Request checklist:

• I've named my PR in the form of "Fixes #issue. Terse description."
• My code follows the style guidelines of Terminal.Gui - if you use Visual Studio, hit CTRL-K-D to automatically reformat your files before committing.
• My code follows the Terminal.Gui library design guidelines
• I ran dotnet test before commit
• I have made corresponding changes to the API documentation (using /// style comments)
• My changes generate no new warnings
• I have checked my code and corrected any poor grammar or misspellings
• I conducted basic QA to assure all features are working

[tig]

Go ahead an update all packages that can be upgraded in this PR, please.

[BDisp]

Go ahead an update all packages that can be upgraded in this PR, please.

Done.