[skip ci] Mark problematic openssl tests as xfail for now

ext/openssl/tests/openssl_error_string_basic_openssl3.phpt

@@ -6,6 +6,7 @@ openssl
 <?php
 if (OPENSSL_VERSION_NUMBER < 0x30000000) die('skip For OpenSSL >= 3.0');
 ?>
+--XFAIL--
 --FILE--
 <?php
 // helper function to check openssl errors

ext/openssl/tests/openssl_private_decrypt_basic.phpt

@@ -2,6 +2,7 @@
 openssl_private_decrypt() tests
 --EXTENSIONS--
 openssl
+--XFAIL--
 --FILE--
 <?php
 $data = "Testing openssl_public_decrypt()";