REL: 3.9.3

This is the third bugfix release of the 3.9.x series.

This release contains several bug-fixes and adjustments:

- Fix `axline` with extremely small slopes
- Fix `axline` with non-linear axis scales
- Fix `minimumSizeHint` with Qt backend
- Fix config directory usage when it's behind a symlink
- Fix draggable legend when blitting is enabled
- Fix high CPU utilization in the `macosx` backend
- Fix multiple hatch `edgecolors` passed to `contourf`
- Improve compatibility with `pytest` 8.2.0