Update Six Labors Refs

[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

This pull request updates third-party dependencies in the ImageSharp.Drawing project to use newer stable versions.

Dependency updates:

• Updated SixLabors.Fonts package from version 3.0.1-alpha.0.19 to 3.1.0, moving from an alpha to a stable release.
• Updated SixLabors.ImageSharp package from version 4.0.1-alpha.0.24 to 4.1.0, moving from an alpha to a stable release.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79%. Comparing base (9dec1a0) to head (431a675).

Additional details and impacted files

@@ Coverage Diff @@## main #414 +/- ##
=====================================
- Coverage 79% 79% -1% 
=====================================
Files 232 232 Lines 27356 27356 Branches 3113 3113 =====================================
- Hits 21874 21873 -1 
Misses 4589 4589 - Partials 893 894 +1 

Flag	Coverage Δ
unittests	79% <ø> (-1%)	⬇️

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