Bump System.Text.Encoding.CodePages from 7.0.0 to 8.0.0

Bumps [System.Text.Encoding.CodePages](https://github.com/dotnet/runtime) from 7.0.0 to 8.0.0.
- [Release notes](https://github.com/dotnet/runtime/releases)
- [Commits](dotnet/runtime@v7.0.0...v8.0.0)

---
updated-dependencies:
- dependency-name: System.Text.Encoding.CodePages
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

src/ShukujitsuSharp.Generator/ShukujitsuSharp.Generator.csproj

@@ -8,7 +8,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="System.Text.Encoding.CodePages" Version="7.0.0" />
+    <PackageReference Include="System.Text.Encoding.CodePages" Version="8.0.0" />
   </ItemGroup>
 
   <ItemGroup>