IMO I would mention the other travel in your SOP but I wouldn't add copies of previous visas, if they question the previous travel and want proof then provide it at that time. You are applying for a study visa not a visitor visa, with a visitor visa you definitely would want to add all the travel history. Your application approval will partly be based on whether they think you will return home but the main focus is the study aspect. If you have a strong SOP in your app that shows you are doing appropriate courses to further your career progression in your home country when you complete the course is more important than your past travel history. That, in a large part, shows your intention to return home after studying.
Have you ever applied to enter Canada before on any type of visa?