Use add_action for action hooks, not add_filter

[GaryJones]

• extended-cpts/src/class-extended-cpt.php

  Line 202 in 3289303

  add_filter( 'pre_get_posts', [ $this, 'maybe_sort_by_fields' ] );

• extended-cpts/src/class-extended-cpt-admin.php

  Line 72 in f1c57ce

  add_filter( 'pre_get_posts', [ $this, 'maybe_filter' ] );

These two lines have got add_filter( 'pre_get_posts', ... ); instead of add_action().

While at the PHP level it makes no difference, we have a VIPCS sniff that specifically looks for filter hook callbacks to ensure that they have a returned value, and the incorrect function call is causing false positives.

There may be others as well, but these are two that stood out immediately.

[johnbillion]

Thanks for the report. Related: WordPress/WordPress-Coding-Standards#713