Plot always zooms out when changing data aspect

[saecki]

This is a regression, I mentioned the original bug in this issue: #1174
and it was fixed in the linked PR: #1184

Seems like this PR broke it #1865 in plot/mod.rs line 723-728.
If no axis is linked it will always expand.

egui/crates/egui/src/widgets/plot/mod.rs

Line 835 in 29fa633

transform.set_aspect_by_expanding(data_aspect as f64);

In the else case change_x should probably be defaulted to false as before.

[saecki]

I don't know how that will impact the issue with the auto bounds though