Add type annotation

Author: sebastianbergmann

build/scripts/generate-global-assert-wrappers.php

@@ -208,6 +208,9 @@ function returnValue(mixed $value): ReturnStub
 }
 
 if (!function_exists('PHPUnit\Framework\returnValueMap')) {
+    /**
+     * @param array<mixed> $valueMap
+     */
     function returnValueMap(array $valueMap): ReturnValueMapStub
     {
         return new ReturnValueMapStub($valueMap);