Correct the return type of wxPersistenceManager methods in the documentation.

DisableSaving() and DisableRestoring() don't return anything.

Closes #14170.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@71075 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

interface/wx/persist.h

@@ -57,7 +57,7 @@ public:
 
         @see DisableRestoring()
      */
-    bool DisableSaving();
+    void DisableSaving();
 
     /**
         Globally disable restoring the persistence object properties.
@@ -67,7 +67,7 @@ public:
 
         @see DisableSaving()
      */
-    bool DisableRestoring();
+    void DisableRestoring();
 
 
     /**