Bump pyjwt from 1.5.3 to 2.4.0 in /requirements

Bumps [pyjwt](https://github.com/jpadilla/pyjwt) from 1.5.3 to 2.4.0.
- [Release notes](https://github.com/jpadilla/pyjwt/releases)
- [Changelog](https://github.com/jpadilla/pyjwt/blob/master/CHANGELOG.rst)
- [Commits](jpadilla/pyjwt@1.5.3...2.4.0)

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

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Author: dependabot[bot]

requirements/base.txt

@@ -22,7 +22,7 @@ Pillow==8.3.2
 premailer
 populus
 psycopg2-binary==2.7.5
-PyJWT==1.5.3
+PyJWT==2.4.0
 PyPdf2
 python-twitter==3.2
 sendgrid==5.6.0