More phpstan fixes

Author: aristath

classes/utils/class-date.php

@@ -18,10 +18,7 @@ class Date {
 	 * @param \DateTime $start_date The start date.
 	 * @param \DateTime $end_date   The end date.
 	 *
-	 * @return array [
-	 *                 'start_date' => \DateTime,
-	 *                 'end_date'   => \DateTime,
-	 *               ].
+	 * @return array <'start_date' => \DateTime, 'end_date' => \DateTime>
 	 */
 	public function get_range( $start_date, $end_date ) {
 		$dates = \iterator_to_array( new \DatePeriod( $start_date, new \DateInterval( 'P1D' ), $end_date ), false );