[REF] Minor parameter simplification

[eileenmcnaughton]

The only value in this array used in the function is 'custom' which should be an array. I think it woul
d only ever be an array or NULL (which would then be an array with this change) but I left
a deprecation notice in case. Pass-by-ref isn't needed

Overview

A brief description of the pull request. Keep technical jargon to a minimum. Hyperlink relevant discussions.

Before

What is the old user-interface or technical-contract (as appropriate)?
For optimal clarity, include a concrete example such as a screenshot, GIF (LICEcap, SilentCast), or code-snippet.

After

What changed? What is new old user-interface or technical-contract?
For optimal clarity, include a concrete example such as a screenshot, GIF (LICEcap, SilentCast), or code-snippet.

Technical Details

If the PR involves technical details/changes/considerations which would not be manifest to a casual developer skimming the above sections, please describe the details here.

Comments

Anything else you would like the reviewer to note

[civibot]

(Standard links)

• If this is your first pull-request for CiviCRM, please browse CONTRIBUTING.md for information about the development and testing processes.
• If you are reviewing this pull-request, you may wish to consult the test sites and the Review Standards (long template, short template).

[seamuslee001]

This seems fine to me