How do you properly remove "REQUIRE SSL" from a single user?
What you are looking for does not exist in MySQL 5.5

Unfortunately, the ALTER USER command for MySQL 5.6 is limited. All you can do is

ALTER USER user@host PASSWORD EXPIRE;


In MySQL 5.7, you could run the ALTER USER command as follows

ALTER USER user@host REQUIRE NONE;


When it comes to MySQL 5.5, you did the most expedient way possible. Great !!!

A more politically correct way would have been to do the following:

DROP USER user@host;
CREATE USER user@host;
GRANT ... on ... TO user@host IDENTIFIED BY '...';


Otherwise, I commend you for doing what was needed.