Bump gunicorn from 19.9.0 to 20.0.4 in /requirements (#5904)

Bumps [gunicorn](https://github.com/benoitc/gunicorn) from 19.9.0 to 20.0.4.
- [Release notes](https://github.com/benoitc/gunicorn/releases)
- [Commits](https://github.com/benoitc/gunicorn/compare/19.9.0...20.0.4)

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

requirements/common.txt

@@ -1,8 +1,8 @@
 # Packages that are shared between deployment and dev environments.
 
-gunicorn==19.9.0 \
-    --hash=sha256:aa8e0b40b4157b36a5df5e599f45c9c76d6af43845ba3b3b0efe2c70473c2471 \
-    --hash=sha256:fa2662097c66f920f53f70621c6c58ca4a3c4d3434205e608e121b5b3b71f4f3
+gunicorn==20.0.4 \
+    --hash=sha256:cd4a810dd51bf497552cf3f863b575dabd73d6ad6a91075b65936b151cbf4f9c \
+    --hash=sha256:1904bb2b8a43658807108d59c3f3d56c2b6121a701161de0ddf9ad140073c626
 
 whitenoise[brotli]==5.0.1 \
     --hash=sha256:62556265ec1011bd87113fb81b7516f52688887b7a010ee899ff1fd18fd22700 \