build(deps): Bump System.Text.Json in /tests/OrasProject.Oras.Tests

Bumps [System.Text.Json](https://github.com/dotnet/runtime) from 8.0.2 to 8.0.3.
- [Release notes](https://github.com/dotnet/runtime/releases)
- [Commits](dotnet/runtime@v8.0.2...v8.0.3)

---
updated-dependencies:
- dependency-name: System.Text.Json
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

src/OrasProject.Oras/OrasProject.Oras.csproj

@@ -23,7 +23,7 @@
 		</AssemblyAttribute>
 	</ItemGroup>
 	<ItemGroup>
-		<PackageReference Include="System.Text.Json" Version="8.0.2" />
+		<PackageReference Include="System.Text.Json" Version="8.0.3" />
 	</ItemGroup>
 	<ItemGroup>
 		<None Include="README.md" Pack="true" PackagePath="/" />