[DOCS] Add alt-text codeblock to Images for Userguide: security.rst

Please confirm the following

• I agree to follow this project's code of conduct.
• I have checked the current issues for duplicates.
• I understand that AWX is open source software provided for free and that I might not receive a timely response.
• I am NOT reporting a (potential) security vulnerability. (These should be emailed to security@ansible.com instead.)

Bug Summary

We need to add alt-text to images for accessibility purposes. See the syntax in the Expected Results below.

AWX version

latest

Select the relevant components

• UI
• UI (tech preview)
• API
• Docs
• Collection
• CLI
• Other

Installation method

kubernetes

Modifications

no

Ansible version

No response

Operating system

No response

Web browser

No response

Steps to reproduce

1. Clone the AWX repo.
2. Navigate to the source files for the User Guide in GitHub at: https://github.com/ansible/awx/tree/devel/docs/docsite/rst/userguide (locally they should reside in /Users/you/awx/docs/docsite/rst/userguide).
3. Open the security.rst file to edit it. Search all image directives and place the :alt: code block beneath it. See syntax in Expected Results below.
4. Commit the changes, open a PR.

Expected results

The following codeblock added to each image with its specific descriptors filled in:

.. image:: ../common/images/image-filename.png
   :alt: Phrase that describes image

or

|Resource - alt text describing image|

.. |Resource - alt text describing image| image:: ../common/images/image-filename.png
   :alt: Phrase that describes image

Actual results

Some images don't have the alt text info in them.

Additional information

Example from Credentials section of the User Guide:

Add Team Permissions
^^^^^^^^^^^^^^^^^^^^^^

To add permissions to a Team:

1. Click the **Add** button, which opens the Add Permissions Wizard.

.. image:: ../common/images/teams-users-add-permissions-form.png 
   :alt: Add Permissions Form