Bump System.Text.Json from 7.0.2 to 7.0.3 in /src (#384)

Bumps [System.Text.Json](https://github.com/dotnet/runtime) from 7.0.2 to 7.0.3.
- [Release notes](https://github.com/dotnet/runtime/releases)
- [Commits](dotnet/runtime@v7.0.2...v7.0.3)

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

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

src/NServiceBus.Json/NServiceBus.Json.csproj

@@ -5,7 +5,7 @@
   </PropertyGroup>
   <ItemGroup>
     <PackageReference Include="NServiceBus" Version="8.0.3" />
-    <PackageReference Include="System.Text.Json" Version="7.0.2" />
+    <PackageReference Include="System.Text.Json" Version="7.0.3" />
     <PackageReference Include="Polyfill" Version="1.23.0" PrivateAssets="all" />
     <PackageReference Include="ProjectDefaults" Version="1.0.90" PrivateAssets="all" />
     <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.1.1" PrivateAssets="All" Condition="$(Configuration) == 'Release'" />