It’s not necessary for every PhD candidate to cite their examiners in their thesis.
It might be helpful for you in particular to have cited your examiners. Or rather, who you have cited might have an influence on the list of academics who might be considered to be good choices for your examiners.
If, as it turns out, you have cited your examiners then it’s worth looking at their work again during your prep for the viva. Be sure of how you have made use of their work in your own.
If, as it turns out, you have not cited your examiners then it will help you to take a look at their while you get ready. Get a sense of what they do and how it connects with your work, if at all.
You don’t need to cite your examiners in order for them to be good choices. You do need to read their work as part of getting ready, regardless of whether or not you have cited them before.