Your version does not support that character set, I believe it was 5.5.3 that introduced it. You should upgrade your mysql to the version you used to export this file.
The error is then quite clear: you set a certain character set in your code, but your mysql version does not support it, and therefore does not know about it.
According to https://dev.mysql.com/doc/refman/5.5/en/charset-unicode-utf8mb4.html :
utf8mb4 is a superset of utf8
so maybe there is a chance you can just make it utf8, close your eyes and hope, but that would depend on your data, and I’d not recommend it.