Bump matplotlib from 3.1.3 to 3.2.1

Bumps [matplotlib](https://github.com/matplotlib/matplotlib) from 3.1.3 to 3.2.1.
- [Release notes](https://github.com/matplotlib/matplotlib/releases)
- [Commits](matplotlib/matplotlib@v3.1.3...v3.2.1)

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

Author: dependabot-preview[bot]

poetry.lock

@@ -67,7 +67,7 @@ showcontent = false
 python = "^3.6"
 boto3 = "^1.12"
 requests = "^2.23"
-matplotlib = "~3.1"
+matplotlib = ">=3.1,<3.3"
 attrs = "~19.3"
 jsonpickle = "~1.3"
 redis = "^3.4"