Enable doc generation for source-build (#59937)

Author: MichaelSimons

Build.proj

@@ -10,7 +10,7 @@
   <Import Project="$(RepositoryEngineeringDir)SubsetValidation.targets" />
 
   <!-- Upfront restore hooks -->
-  <Import Project="$(RepositoryEngineeringDir)restore\docs.targets" Condition="'$(DotNetBuildFromSource)' != 'true'" />
+  <Import Project="$(RepositoryEngineeringDir)restore\docs.targets" />
   <Import Project="$(RepositoryEngineeringDir)restore\optimizationData.targets" Condition="'$(DotNetBuildFromSource)' != 'true'" />
 
   <Target Name="BuildLocalTasks"