fix: include the original project file instead of Fable.Package.SDK.targets

Author: MangelMaxime

src/build/Fable.Package.SDK.targets

@@ -8,7 +8,7 @@
         <Content Include="@(Compile)" Pack="true"
             PackagePath="fable/%(RelativeDir)%(Filename)%(Extension)" />
         <!-- Include the project file itself as well -->
-        <Content Include="$(MSBuildThisFileFullPath)" Pack="true" PackagePath="fable/" />
+        <Content Include="$(MSBuildProjectFullPath)" Pack="true" PackagePath="fable/" />
     </ItemGroup>
     <!--
         Automatically add Fable tags