docs: Add missing AXES_IPWARE_PROXY_ORDER setting documentation

[ram98kgp]

What does this PR do?

This PR adds documentation for the AXES_IPWARE_PROXY_ORDER setting, which currently exists in the
codebase but is missing from the official configuration documentation.

Problem

The AXES_IPWARE_PROXY_ORDER setting is defined in axes/conf.py with a default value of "left-most"
and is used in axes/helpers.py to configure IP detection behavior, but it's not documented in
docs/4_configuration.rst alongside other AXES_IPWARE_* settings like AXES_IPWARE_PROXY_COUNT and
AXES_IPWARE_META_PRECEDENCE_ORDER.
This can lead to confusion for users deploying behind reverse proxies who may not be aware this
configuration option exists.

Solution

Added comprehensive documentation for AXES_IPWARE_PROXY_ORDER including:

• Default value and valid options ("left-most" or "right-most")

Related

• Source code reference:
  axes/conf.py#L153-L157

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
• Did you make sure to update the documentation with your changes?
• Did you write any new necessary tests? (N/A - documentation only)