REL: v3.4.3

This is the third bugfix release of the 3.4.x series.

This release contains several critical bug-fixes:

* Clarify deprecation of `Axes.figbox`
* Disable `MultiCursor` widget on `Axes` subplots which it is not tracking
* Don't simplify path in `LineCollection.get_segments`
* Fix DPI in subfigures, affecting tick spacing, and scatter marker size
* Fix broken EPS output when using Type 42 STIX fonts
* Fix change in tick behaviour when calling `Axes.clear`
* Fix class docstrings for `Norm`s created from `Scale`s
* Fix compatibility with NumPy 1.21.0
* Fix crash on broken TrueType fonts
* Fix incorrect hits from `Path.intersects_path`
* Fix leak if affine_transform is passed invalid vertices
* Fix legends of `stackplot` with `edgecolors='face'`
* Fix plot directive when building in parallel
* Fix `supxlabel` and `supylabel` behaviour in constrained layout
* Fix tests with latest Inkscape and Ghostscript
* Improve `DateFormatter` styling for month names when `usetex=True`
* Re-disable autoscaling after interactive zoom
* Work around bug in Pillow 8.3.0