Fix distributedcloud openstack-tox-docs

[Hugo Nicodemos Brito]

Brief Description
-----------------
The openstack-tox-docs fails with: Invalid configuration value found: 'language = None'. Update your configuration to a valid language code. Falling back to 'en' (English).

Severity
--------
<Critical: System/Feature is not usable due to the defect>

Steps to Reproduce
------------------
Commit a change

Expected Behavior
------------------
All zuul jobs pass.

Actual Behavior
----------------
openstack-tox-docs failed.

Reproducibility
---------------
<Reproducible>

System Configuration
--------------------
<One node system, Two node system, Multi-node system, Dedicated storage, https, IPv4, IPv6 etc.>

Branch/Pull Time/Commit
-----------------------
master

Last Pass
---------
NA

Timestamp/Logs
--------------
NA

Test Activity
-------------
NA

Workaround
----------
NA

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/c/starlingx/distcloud/+/893069

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/starlingx/distcloud/+/893069
Committed: https://opendev.org/starlingx/distcloud/commit/ab0581157087460e3caa08fd0207087143893fcf
Submitter: "Zuul (22348)"
Branch: master

commit ab0581157087460e3caa08fd0207087143893fcf
Author: Hugo Brito <email address hidden>
Date: Tue Aug 29 11:45:59 2023 -0300

    Fix distributedcloud openstack-tox-docs

    This change the default docs language conf to 'en'
    instead of None.

    Closes-Bug: 2033410

    Change-Id: I24a47c6e817f977fbb49c81a14da4300223e397f
    Signed-off-by: Hugo Brito <email address hidden>