Incorrect flag name for confirming WP version update

[darylldoyle]

The get_should_update_wp() method of the pull command uses flag called update_wp to allow bypassing the "Do you want to update WP" question.

snapshots/includes/classes/WPCLICommands/Pull.php

Lines 354 to 358 in 9bc9f3f

	return $wp_version !== $this->get_meta()['wp_version'] && $this->prompt->get_flag_or_prompt(
	$this->get_assoc_args(),
	'update_wp',
	'This snapshot is running WordPress version ' . $this->get_meta()['wp_version'] . ', and you are running version ' . $wp_version . '. Do you want to change your version to match the snapshot?'
	);

The pull command doesn't list this as a valid flag and instead lists it as confirm_wp_version_change.

We should update the flag used by the method to match the one defined by the flag.