Bump System.Text.Json from 7.0.3 to 8.0.3 in /build

Bumps [System.Text.Json](https://github.com/dotnet/runtime) from 7.0.3 to 8.0.3.
- [Release notes](https://github.com/dotnet/runtime/releases)
- [Commits](dotnet/runtime@v7.0.3...v8.0.3)

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

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

build/build.csproj

@@ -8,7 +8,7 @@
   <ItemGroup>
     <PackageReference Include="Bullseye" Version="4.2.1" />
     <PackageReference Include="SimpleExec" Version="11.0.0" />
-    <PackageReference Include="System.Text.Json" Version="7.0.3" />
+    <PackageReference Include="System.Text.Json" Version="8.0.3" />
   </ItemGroup>
 
 </Project>