MNT Fix PHP linting in test class

[GuySartorelli]

Fixes linting problem in https://github.com/silverstripe/silverstripe-framework/actions/runs/13847305384/job/38748285260

 FILE: ...ework/tests/php/Forms/HTMLEditor/HTMLEditorConfigTest/NullEditorConfig.php
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FOUND 2 ERRORS AFFECTING 1 LINE
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 52 | ERROR | [x] Opening brace should be on a new line
 52 | ERROR | [x] Closing brace must be on a line by itself
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Issue

• Broken builds, merge-ups, and licenses .github#377