Bump matplotlib from 3.2.1 to 3.2.2 (#1650)

Bumps [matplotlib](https://github.com/matplotlib/matplotlib) from 3.2.1 to 3.2.2.
- [Release notes](https://github.com/matplotlib/matplotlib/releases)
- [Commits](https://github.com/matplotlib/matplotlib/compare/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>

requirements.txt

@@ -4,7 +4,7 @@ imbalanced-learn==0.7.0
 joblib==0.15.1
 libmozdata==0.1.68
 lmdb==0.98
-matplotlib==3.2.1
+matplotlib==3.2.2
 mercurial==5.3.2
 microannotate==0.0.20
 mozci==1.6.1