Update mentions of psycopg in comments

[Eraldo]

Description

Removing the comments mentioning psycopg2 as it has been upgraded in a previous commit: https://github.com/cookiecutter/cookiecutter-django/pull/4421/files

Checklist:

• I've made sure that tests are updated accordingly (especially if adding or updating a template option)
• I've updated the documentation or confirm that my change doesn't require any updates

I also checked that the dependency mentioned is still needed with psycopg3.
Source: https://www.psycopg.org/psycopg3/docs/basic/install.html

PostgreSQL client development headers (e.g. the libpq-dev package).

Rationale

Updated comments.