Fix mysql_list_fields.phpt test

The minimum length is given in bytes, so it is charset dependent.
For utf8 charsets for example it's 3 rather than 1.

Author: nikic

ext/mysql/tests/mysql_list_fields.phpt

@@ -74,7 +74,7 @@ mysql_field_name(): id
 mysql_field_type(): int
 Field Offset 1
 mysql_field_flags()%s
-mysql_field_len(): 1
+mysql_field_len(): %s
 mysql_field_name(): label
 mysql_field_type(): string
 done!