Bump babel from 2.8.0 to 2.9.1

Bumps [babel](https://github.com/python-babel/babel) from 2.8.0 to 2.9.1.
- [Release notes](https://github.com/python-babel/babel/releases)
- [Changelog](https://github.com/python-babel/babel/blob/master/CHANGES)
- [Commits](python-babel/babel@v2.8.0...v2.9.1)

---
updated-dependencies:
- dependency-name: babel
  dependency-type: direct:production
...

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Author: dependabot[bot]

requirements-python37-rf31.txt

@@ -7,7 +7,7 @@ alabaster==0.7.12
 appdirs==1.4.3
 astroid==2.4.0
 attrs==19.3.0
-babel==2.8.0
+babel==2.9.1
 backcall==0.1.0
 black==19.10b0
 bleach==3.3.0

requirements-python37-rf32.txt

@@ -7,7 +7,7 @@ alabaster==0.7.12
 appdirs==1.4.3
 astroid==2.4.0
 attrs==19.3.0
-babel==2.8.0
+babel==2.9.1
 backcall==0.1.0
 black==19.10b0
 bleach==3.3.0