Update the wxSpinCtrlDouble documentation so SetIncrement refers to SetDigits

Closes #12342

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@72514 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

interface/wx/spinctrl.h

@@ -308,6 +308,8 @@ public:
 
     /**
         Sets the increment value.
+        @note You may also need to increase the number of visible digits
+        using SetDigits
     */
     void SetIncrement(double inc);