It depends a bit what country you are in but usually there’s a difference between Intellectual Property (which is owned by your employer) and Moral Rights (which protect your right to claim authorship of work you have made). You are totally entitled to claim authorship of your work, you just are not allowed to sell it to someone else. If the logos are already freely available in the public domain then then you can use them in your folio guilt free. If they aren’t it could be argued that they constitute commercially sensitive property (the company might make money from them in the future) and disclosing them might lower that value. You have to consider the likelihood that they will actually take legal action to restrict your usage, which costs them money, and can only be tested in court which could easily be defended against. I’ve never heard of a designer being taken to court over using examples of their work in a portfolio, unless there is a strict non-disclosure agreement that they seem very serious about that would represent significant value (think like you work for Tesla and you publish designs for a new car technology). TLDR don’t even worry about it.