Update matplotlib requirement from ~=3.2.1 to ~=3.2.2 (#605)

Updates the requirements on [matplotlib](https://github.com/matplotlib/matplotlib) to permit the latest version.
- [Release notes](https://github.com/matplotlib/matplotlib/releases)
- [Commits](matplotlib/matplotlib@v3.2.1...v3.2.2)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

Author: dependabot-preview[bot]

requirements-dev.txt

@@ -5,7 +5,7 @@ pytest ~=5.4.3
 vcrpy ~=4.0.2
 doctr ~=1.8.0
 ipython ~=7.15.0
-matplotlib ~=3.2.1
+matplotlib ~=3.2.2
 numpydoc ~=1.0.0
 requests-mock ~=1.8.0
 sphinx ~=2.4.4