Until Smartsheet fixes this, my solution for clients is to set the font for the axis with the percentages to be white which removes it (Highlighted area below). Then I add the value label to the series with the percent I want to display. When I do this to show progress, I use a stacked chart to show the remaining percentage (= 1-percentage I want displayed) and do not label the second series. Below is an example of progress against deliverables for a project plan. You may need to use bar chart vs. column if you find the series label is too crowded.
https://us.v-cdn.net/6031209/uploads/DY5LFZPJIFNM/image.png
If you want more info, find me on Linked In under Kristine Candela, and connect - I am happy to help!