Revert "Fix duplicate test case"

This reverts commit fdd4e84.

Author: youkidearitai

ext/mbstring/tests/gh20674.phpt

@@ -19,11 +19,22 @@ $subject = "=?us-ascii?Q?The_PH?= \t =?us-ascii?Q?P_8.5?=";
 var_dump(mb_decode_mimeheader($subject));
 
 // from RFC 2047 https://www.ietf.org/rfc/rfc2047
-var_dump(mb_decode_mimeheader("(=?ISO-8859-1?Q?a?= =?ISO-8859-1?Q?_b?=)"));
+var_dump(mb_decode_mimeheader("(=?ISO-8859-1?Q?a?= =?ISO-8859-2?Q?_b?=)"));
+var_dump(mb_decode_mimeheader("(=?ISO-8859-1?Q?a_b?=)"));
+var_dump(mb_decode_mimeheader("(=?ISO-8859-1?Q?a?=  =?ISO-8859-1?Q?b?=)"));
+var_dump(mb_decode_mimeheader("(=?ISO-8859-1?Q?a?= b)"));
+var_dump(mb_decode_mimeheader("(=?ISO-8859-1?Q?a?=  =?ISO-8859-1?Q?b?=)"));
+var_dump(mb_decode_mimeheader("(=?ISO-8859-1?Q?a?=
+	=?ISO-8859-1?Q?b?=)"));
 ?>
 --EXPECTF--
 string(11) "The PHP 8.5"
 string(11) "The PHP 8.5"
 string(11) "The PHP 8.5"
 string(11) "The PHP 8.5"
 string(5) "(a b)"
+string(5) "(a b)"
+string(4) "(ab)"
+string(5) "(a b)"
+string(4) "(ab)"
+string(4) "(ab)"