Revert "Avoid round-trip through sourceModule in scalacLinkedClass."

This reverts commit e88c5b7.

Fixes scala#9916

Author: griggt

compiler/src/dotty/tools/dotc/core/SymDenotations.scala

@@ -1176,7 +1176,7 @@ object SymDenotations {
 
     final def scalacLinkedClass(using Context): Symbol =
       if (this.is(ModuleClass)) companionNamed(effectiveName.toTypeName)
-      else if (this.isClass) companionNamed(effectiveName.moduleClassName)
+      else if (this.isClass) companionNamed(effectiveName.moduleClassName).sourceModule.moduleClass
       else NoSymbol
 
     /** Find companion class symbol with given name, or NoSymbol if none exists.