The Filament-3-→-5 namespace shim used class_exists($legacy, false),
which skips the autoloader. At composer-autoload time NO Filament
classes are loaded yet, so the check ALWAYS returned false — meaning
even on Filament 3 (where Filament\Tables\Actions\Action is a real
175-line class on disk) the shim aliased it to Filament\Actions\Action
(the v5 unified class).

Result: Filament 3's table builder calls $action->table($this) on every
filter/header/row action, but the aliased v5 class has no ->table()
method, blowing up every table render with:

    Method Filament\Actions\Action::table does not exist

Fix: drop the `false` so class_exists triggers the autoloader and
finds the v3 class file when present, leaving the alias unset.

Verified on tyregeneral-jobcard-application (Filament 3.x) which was
hitting this on every issues page load.