Fix FSharp.Core reference (#15244)

Author: auduchinok

src/FSharp.Compiler.Interactive.Settings/FSharp.Compiler.Interactive.Settings.fsproj

@@ -34,8 +34,12 @@
     <Compile Include="fsiaux.fs" />
   </ItemGroup>
 
-  <ItemGroup>
-    <ProjectReference Include="..\FSharp.Core\FSharp.Core.fsproj" />
+  <ItemGroup Condition="'$(FSHARPCORE_USE_PACKAGE)' != 'true'">
+    <ProjectReference Include="$(FSharpSourcesRoot)\FSharp.Core\FSharp.Core.fsproj" />
+  </ItemGroup>
+
+  <ItemGroup Condition="'$(FSHARPCORE_USE_PACKAGE)' == 'true'">
+    <PackageReference Include="FSharp.Core" Version="$(FSharpCoreShippedPackageVersionValue)" />
   </ItemGroup>
 
 </Project>