nuget: bump SkiaSharp.NativeAssets.Linux and SkiaSharp

Bumps [SkiaSharp.NativeAssets.Linux](https://github.com/mono/SkiaSharp) and [SkiaSharp](https://github.com/mono/SkiaSharp). These dependencies needed to be updated together.

Updates `SkiaSharp.NativeAssets.Linux` from 2.88.7 to 2.88.8
- [Release notes](https://github.com/mono/SkiaSharp/releases)
- [Commits](mono/SkiaSharp@v2.88.7...v2.88.8)

Updates `SkiaSharp` from 2.88.7 to 2.88.8
- [Release notes](https://github.com/mono/SkiaSharp/releases)
- [Commits](mono/SkiaSharp@v2.88.7...v2.88.8)

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

Signed-off-by: dependabot[bot] <support@github.com>

Directory.Packages.props

@@ -42,8 +42,8 @@
     <PackageVersion Include="Silk.NET.Vulkan" Version="2.21.0" />
     <PackageVersion Include="Silk.NET.Vulkan.Extensions.EXT" Version="2.21.0" />
     <PackageVersion Include="Silk.NET.Vulkan.Extensions.KHR" Version="2.21.0" />
-    <PackageVersion Include="SkiaSharp" Version="2.88.7" />
-    <PackageVersion Include="SkiaSharp.NativeAssets.Linux" Version="2.88.7" />
+    <PackageVersion Include="SkiaSharp" Version="2.88.8" />
+    <PackageVersion Include="SkiaSharp.NativeAssets.Linux" Version="2.88.8" />
     <PackageVersion Include="SPB" Version="0.0.4-build32" />
     <PackageVersion Include="System.IO.Hashing" Version="8.0.0" />
     <PackageVersion Include="System.Management" Version="8.0.0" />