Piracy is ill-defined and so it's hard to say what is or isn't for such an informal term, but even if it weren't: removing the DRM of stuff you purchased legally, and for your own use, is not "piracy" by any reasonable use of the word.
I think most people's definition is roughly "obtaining and consuming media you haven't paid for in violation of copyright." Sometimes it's just about obtaining something in violation of copyright, even if you've already bought it (e.g. "I always buy things and then pirate them anyway because I hate the DRM but still want to support the creators."). Very few would consider stripping DRM on files you already have to be piracy, even if the DMCA forbids it, because the vast majority of people consider transfer of copyrighted material to be foundational to the meaning of the word.
Piracy is ill-defined and so it's hard to say what is or isn't for such an informal term, but even if it weren't: removing the DRM of stuff you purchased legally, and for your own use, is not "piracy" by any reasonable use of the word.
It might be illegal, but it's not piracy.