BUG: Outdated README

[akrymets]

Describe the bug
The installation link https://docs.aleph.occrp.org/developers/installation in the README is no more available.

To Reproduce
Steps to reproduce the behavior:

1. Open the repository
2. Scroll down to https://github.com/alephdata/aleph/blob/develop/README.rst?plain=1#L19

Expected behavior
The link leads to an installation page

Aleph version
develop branch