Remove S.T.J dependency for net8.0 (#136)

Remove package reference when targeting `net8.0` (and greater) to instead depend on the in-box reference.

Resolves #134.

Author: martincostello

CHANGELOG.md

@@ -1,5 +1,12 @@
 # Changelog
 
+## Unreleased version
+
+### Bug Fixes
+
+* Remove reference on System.Text.Json for `net8.0` target framework
+  ([#136](https://github.com/grafana/grafana-opentelemetry-dotnet/pull/136))
+
 ## 1.2.0
 
 ### BREAKING CHANGES

src/Grafana.OpenTelemetry.Base/Grafana.OpenTelemetry.Base.csproj

@@ -22,7 +22,7 @@
     <PackageReference Include="Microsoft.Extensions.Configuration" Version="8.0.0" />
     <PackageReference Include="Microsoft.Extensions.Configuration.EnvironmentVariables" Version="8.0.0" />
     <PackageReference Include="Microsoft.Extensions.Logging" Version="8.0.1" />
-    <PackageReference Include="System.Text.Json" Version="8.0.5" />
+    <PackageReference Include="System.Text.Json" Version="8.0.5" Condition="!$([MSBuild]::IsTargetFrameworkCompatible('$(TargetFramework)', 'net8.0'))" />
     <PackageReference Include="MinVer" Version="4.3.0">
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>