Bump pycparser from 2.19 to 2.20

Bumps [pycparser](https://github.com/eliben/pycparser) from 2.19 to 2.20.
- [Release notes](https://github.com/eliben/pycparser/releases)
- [Changelog](https://github.com/eliben/pycparser/blob/master/CHANGES)
- [Commits](eliben/pycparser@release_v2.19...release_v2.20)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Author: dependabot-preview[bot]

requirements.txt

@@ -15,5 +15,5 @@ fonttools==4.4.1
 idna==2.9                 # via yarl
 multidict==4.7.5          # via aiohttp, yarl
 pycares==3.1.1            # via aiodns
-pycparser==2.19           # via cffi
+pycparser==2.20           # via cffi
 yarl==1.4.2               # via aiohttp