So my question is whether I can remove files and the licenses going with those files?
Yes you can.
Nearly all copyright licenses state, in one form or another, that you must keep the license notices and/or license text.
What is meant is that,
- for the notices in a source file, you must keep those notices as long as there is any content in the file that is covered by the license referred to in the notice. As soon as all covered content is deleted, you can also delete that notice and/or remove the file.
- for license files, you must keep them as long as there is any content in the project that is covered by the license. As soon as you removed the last content that was governed by the license from the project, you can also remove the file(s) with the license text and attribution notices.