Psalm: remove suppression of return type issue

 ... and fix it instead.

Author: jrfnl

psalm.xml

@@ -42,18 +42,6 @@
             </errorLevel>
         </RedundantConditionGivenDocblockType>
 
-        <InvalidReturnType>
-            <errorLevel type="info">
-                <file name="src/Utils.php"/>
-            </errorLevel>
-        </InvalidReturnType>
-
-        <InvalidReturnStatement>
-            <errorLevel type="info">
-                <file name="src/Utils.php"/>
-            </errorLevel>
-        </InvalidReturnStatement>
-
         <ArgumentTypeCoercion>
             <errorLevel type="info">
                 <!-- PHP handles invalid preg_split flags just fine. -->

src/Utils.php

@@ -42,7 +42,8 @@ abstract class Utils
      *      Note that this changes the return value in an array where every element is an array consisting of the
      *      matched string at offset 0 and its string offset into subject at offset 1.
      *
-     * @return string[] Returns an array containing substrings of subject split along boundaries matched by pattern
+     * @return array<int|string, array<int|string, string>> Returns an array containing substrings of subject
+     *                                                      split along boundaries matched by pattern
      *
      * @throws PcreException
      */