Sure, but in this case Apple isn't being accused of anything so the 5th amendment doesn't apply.

"nor shall be compelled in any criminal case to be a witness against himself" (https://www.law.cornell.edu/wex/fifth_amendment)

This is a criminal case, however. It would apply to real people, but likely does not apply to corporations regardless of rulings treating corporations as people for other purpose. I imagine the Apple lawyers would have had it as part of their defense strategy if it did.

No one is asking Apple to testify against itself.