Having an affair is a personal matter and usually not a reason for deportation under Canadian immigration rules. People are deported if they do crimes, break immigration laws, or lie on their immigration papers.
But, if the husband has proof that the wife lied on her PR application or married him just for immigration purposes, he can report it to immigration officials. Immigration, Refugees, and Citizenship Canada (IRCC) or the Canada Border Services Agency (CBSA) will look into it. If they find out she lied, they may refuse her PR or even deport her in serious cases.
If the affair has nothing to do with immigration fraud, it likely won’t lead to deportation.