Update developer docs for Qubes 4.1

[rocodes]

https://docs.securedrop.org/en/stable/development/qubes_staging.html need to be updated so that:

• the /rw/config/qubes-firewall-user-script changes that allow communication between sd-dev and the staging qubes are moved to the firewall's dvm template (This probably means cloning fedora-36-dvm, but will also conflict with the sd-fedora-dvm that we create during workstation provisioning, so we may have to add that logic conditionally to the workstation dvm provisioning in a development/staging environment...)
• the RPC policy changes are in the new /etc/qubes/policy.d/include directory instead of the previous 4.0 structure

https://docs.securedrop.org/en/stable/development/setup_development.html#qubes need to be updated so that

• sd-dev is based off Debian 11 and python 3.9 support is noted

There may be other changes, but on a quick readthrough this is what sticks out to me

[rocodes]

(Partially addressed by #362)