The argument $callback is not a callable
The callable is in $callback['callable'], so change the type to array
Change-Id: I9b990f2729874b2743cbcc501b97758da5bf8154
/**
* Add an installation step following the given step.
*
- * @param callable $callback A valid installation callback array, in this form:
+ * @param array $callback A valid installation callback array, in this form:
* [ 'name' => 'some-unique-name', 'callback' => [ $obj, 'function' ] ];
* @param string $findStep The step to find. Omit to put the step at the beginning
*/