Bump System.Text.Json from 8.0.3 to 8.0.4 in /src/SharpGLTF.Core

Bumps System.Text.Json from 8.0.3 to 8.0.4.

---
updated-dependencies:
- dependency-name: System.Text.Json
  dependency-type: direct:production
...

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

src/SharpGLTF.Core/SharpGLTF.Core.csproj

@@ -19,7 +19,7 @@
   </ItemGroup>  
   
   <ItemGroup Condition=" '$(TargetFramework)' == 'netstandard2.0' OR '$(TargetFramework)' == 'netstandard2.1'">    
-    <PackageReference Include="System.Text.Json" Version="8.0.3" />
+    <PackageReference Include="System.Text.Json" Version="8.0.4" />
   </ItemGroup>
 
   <ItemGroup>