...version to 3.7.4 (in `buster-backports` too)
```
commit 62041880dd71b8242df179206431803ea8aa8d1a (HEAD -> debian/unstable-swh)
Author: Antoine Lambert <antoine.lambert@inria.fr>
Date: Tue Apr 7 14:03:42 2020 +0200
debian/control: Bump minimal django version to 2.2
python3-django 2.2.11 from buster_backports will now be used in production.
commit 9f170e03d05ca04ee221eb7c3e8d5a029ea8b07b
Author: Antoine Lambert <antoine.lambert@inria.fr>
Date: Tue Apr 7 12:54:46 2020 +0200
debian/control: Bump minimal typing-extensions version to 3.7.4
swh-web uses TypedDict from typing-extensions which is not available in default
buster package (3.7.2).
We need to get 3.7.4 version from buster-backports instead.
commit 803ef79116c9750d273e631ce01ace26ebdedcda
Author: Antoine Lambert <antoine.lambert@inria.fr>
Date: Tue Apr 7 12:33:53 2020 +0200
debian/control: Bump swh depedencies
```
Related to T2303