Bump matplotlib from 3.2.1 to 3.3.1

Bumps [matplotlib](https://github.com/matplotlib/matplotlib) from 3.2.1 to 3.3.1.
- [Release notes](https://github.com/matplotlib/matplotlib/releases)
- [Commits](matplotlib/matplotlib@v3.2.1...v3.3.1)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

requirements.txt

@@ -1,7 +1,7 @@
 # base
 numpy==1.18.1
 scipy==1.4.1
-matplotlib==3.2.1
+matplotlib==3.3.1
 scikit-learn==0.22.1
 six==1.15.0
 Pillow==7.2.0