ext/pcre: fix new pcre2 test

Author: devnexen

ext/pcre/tests/preg_match_all_negative_length_match.phpt

@@ -6,5 +6,5 @@ $result = preg_match_all('/(?=ab\K)a/', 'ab', $matches);
 var_dump($result);
 ?>
 --EXPECTF--
-Warning: preg_match_all(): Get subpatterns list failed in %s on line %d
+Warning: preg_match_all(): Compilation failed: \K is not allowed in lookarounds (but see PCRE2_EXTRA_ALLOW_LOOKAROUND_BSK) at offset %d in %s
 bool(false)

ext/pcre/tests/preg_match_negative_length_match.phpt

@@ -6,5 +6,5 @@ $result = preg_match('/(?=ab\K)a/', 'ab', $matches);
 var_dump($result);
 ?>
 --EXPECTF--
-Warning: preg_match(): Get subpatterns list failed in %s on line %d
+Warning: preg_match_all(): Compilation failed: \K is not allowed in lookarounds (but see PCRE2_EXTRA_ALLOW_LOOKAROUND_BSK) at offset %d in %s
 bool(false)