Undeprecate VariableDescriptorWithAccessors.isDelegated

Apparently there's quite a few valid usages of this method outside of
the compiler frontend, where manual suppression is annoying.

core/descriptors/src/org/jetbrains/kotlin/descriptors/VariableDescriptorWithAccessors.kt

@@ -25,10 +25,10 @@ interface VariableDescriptorWithAccessors : VariableDescriptor {
      * Please be careful with this method. Depending on the fact that a property is delegated may be dangerous in the compiler.
      * Whether or not a property is delegated is neither the API or the ABI of that property, and one should be able to recompile a library
      * in a way that makes some non-delegated properties delegated or vice versa, without any problems at compilation time or at runtime.
+     * So this method should not be used in the compiler frontend in a way that would significantly alter the compilation result.
      *
      * This flag is needed for reflection however, that's why it's serialized to metadata and is exposed in this interface.
      */
-    @Deprecated("Do not call this method in the compiler front-end.")
     val isDelegated: Boolean
 }