WCSAxes Major Formatter Does Not Update When Format Unit is Changed

[DanRyanIrish]

Description

The WCSAxes Major Formatter Does Not Update When Format Unit is Changed.

Expected behavior

Expected behaviour is that the Major formatter updates itself such that an appropriate precision is used by on the units.

Actual behavior

The above does not happen. In the below example, the y axis is stored in the WCS as metres and then changed to nm for the plot. However, as can be seen the precision is kept leading to many extraneous 0s.

[pllim]

What are the versions?

[Cadair]

The plot was made with dev, but I believe that it's the same on all past releases as well.

[astrofrog]

@pllim - you don't have to assign me, @Cadair is an expert too now! :)