rightAxis.labelXOffset moving label up/down on HorizontalBarChartView

* [x] I've read, understood, and done my best to follow the [*CONTRIBUTING guidelines](https://github.com/jjatie/Charts/blob/master/CONTRIBUTING.md).

## What did you do?

Created a `HorizontalBarChartView` and added `rightAxis.labelXOffset`

## What did you expect to happen?

Expected x position of label to changed depending on value.

## What happened instead?

Y position of labels changed.

## Charts Environment

**Charts version/Branch/Commit Number:** 3.6.0
**Xcode version:** 12
**Swift version:** 5.0
**Platform(s) running Charts:** iOS
**macOS version running Xcode:** 10.15.4

## Demo Project

Can be tested on demo project.

`HorizontalBarChartViewController` with `rightAxis.labelXOffset = 0`


`HorizontalBarChartViewController` with `rightAxis.labelXOffset = 10`


Start with the demo project's HorizontalBarChartViewController and reproduce the behavior using rightAxis.labelXOffset values of 0 and 10. Trace how the HorizontalBarChartView renders right-axis labels and determine why the offset changes their Y position instead of X position. Done means the offset changes only the label's X position, verified in the demo on iOS.

Written by the indexing model from the issue text.