Rename the menu option to "Documentation"
Rename the menu option to "Documentation"

This is perhaps more clear to the user as to what it is.

Signed-off-by: Patrick Avery <743342299f279e7a8c3ff5eb40671fce3e95f13a@kitware.com>

OpenChemistry/tomviz,OpenChemistry/tomviz,OpenChemistry/tomviz,OpenChemistry/tomviz