[Tests -> All](deps): Bump SkiaSharp in /Source/SammBot.Tests

Bumps [SkiaSharp](https://github.com/mono/SkiaSharp) from 2.88.6 to 2.88.7.
- [Release notes](https://github.com/mono/SkiaSharp/releases)
- [Commits](mono/SkiaSharp@v2.88.6...v2.88.7)

---
updated-dependencies:
- dependency-name: SkiaSharp
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

Source/SammBot.Library/SammBot.Library.csproj

@@ -9,7 +9,7 @@
     <ItemGroup>
       <PackageReference Include="Discord.Net" Version="3.13.0" />
       <PackageReference Include="Microsoft.EntityFrameworkCore" Version="8.0.1" />
-      <PackageReference Include="SkiaSharp" Version="2.88.6" />
+      <PackageReference Include="SkiaSharp" Version="2.88.7" />
     </ItemGroup>
 
 </Project>