Remove duplicate array shape

DiscriminatorColumnMapping is just a specialization of the array shape
that is right of the pipe: it has the same fields, except fewer fields
are nullable. The union of that is the same thing as the array shape.

Author: greg0ire

lib/Doctrine/ORM/Mapping/ClassMetadataInfo.php

@@ -3131,7 +3131,7 @@ public function addEntityListener($eventName, $class, $method)
      * @see getDiscriminatorColumn()
      *
      * @param mixed[]|null $columnDef
-     * @psalm-param DiscriminatorColumnMapping|array{name: string|null, fieldName?: string, type?: string, length?: int, columnDefinition?: string|null, enumType?: class-string<BackedEnum>|null}|null $columnDef
+     * @psalm-param array{name: string|null, fieldName?: string, type?: string, length?: int, columnDefinition?: string|null, enumType?: class-string<BackedEnum>|null}|null $columnDef
      *
      * @return void
      *