matplotlib 3.3.4

REL: v3.3.4

on Python PyPI

This is the fourth bugfix release of the 3.3.x series.

This release contains several critical bug-fixes:

• Fix WebAgg initialization.
• Fix parsing QT_API setting with mixed case.
• Fix build with link-time optimization disabled in environment.
• Fix test compatibility with NumPy 1.20.
• Fix test compatibility with pytest 6.2.