Support hiding axes labels

[Rookieafnan7]

Currently there is no support for 'none' value for attribute tickLblPos of Axes objects by openpyxl. This is because tickLblPos of class _BaseAxis is set to NestedNoneSet Class which automatically converts 'none' values into None (type) prompting the excel to default to 'nextTo' for Label positioning. Label hiding is a crucial feature, and i implore you to kindly fix this issue at the earliest. Thanks!