Enable source link in nuget packages

It was disabled in #262, but instead of been disabled only for OSx it was never set to be true at first place, so it was off for all platforms.
Regarding OSx it looks like bug was fixed somewhere around 2019 (dotnet/sourcelink#288)

Author: Ivan Matantsev

Directory.Build.props

@@ -12,8 +12,9 @@
     <DebugType>Portable</DebugType>
     <LangVersion>9.0</LangVersion>
     <HighEntropyVA>true</HighEntropyVA>
-    <EnableSourceLink Condition="$([MSBuild]::IsOSPlatform('osx'))">false</EnableSourceLink>
-    <EnableSourceControlManagerQueries>$(EnableSourceLink)</EnableSourceControlManagerQueries>
+    <PublishRepositoryUrl>true</PublishRepositoryUrl>
+    <EmbedUntrackedSources>true</EmbedUntrackedSources>
+    <AllowedOutputExtensionsInPackageBuildOutputFolder>$(AllowedOutputExtensionsInPackageBuildOutputFolder);.pdb</AllowedOutputExtensionsInPackageBuildOutputFolder>
     <!--This will target the latest patch release of the runtime released with the current SDK.  -->
     <TargetLatestRuntimePatch>true</TargetLatestRuntimePatch>
     <RuntimePackageVersion>5.0.0</RuntimePackageVersion>
@@ -22,12 +23,6 @@
     <Hl7FhirVersion>1.9.0</Hl7FhirVersion>
   </PropertyGroup>
 
-  <PropertyGroup Condition=" '$(EnableSourceLink)' == 'true' ">
-    <PublishRepositoryUrl>true</PublishRepositoryUrl>
-    <EmbedUntrackedSources>true</EmbedUntrackedSources>
-    <AllowedOutputExtensionsInPackageBuildOutputFolder>$(AllowedOutputExtensionsInPackageBuildOutputFolder);.pdb</AllowedOutputExtensionsInPackageBuildOutputFolder>
-  </PropertyGroup>
-
   <Choose>
     <When Condition="$(MSBuildProjectName.Contains('Test'))">
       <PropertyGroup>