MNT Fix behat test

[emteknetnz]

Issue silverstripe/.github#99

Fixes
https://github.com/silverstripe/silverstripe-asset-admin/actions/runs/5945064593/job/16123479957?pr=1388#step:12:509

    And I press the "Insert" button                                                 # SilverStripe\BehatExtension\Context\BasicContext::stepIPressTheButton()
      element click intercepted: Element <button aria-label="Insert from Files" title="Insert from Files" type="button" tabindex="-1" class="tox-tbtn" aria-disabled="false" style="width: 34px;">...</button> is not clickable at point (677, 359). Other element would receive the click: <div class="gallery__files">...</div>

[GuySartorelli]

Looks good to me.