mockftpserver: drop .classpath files and update README.txt am: 8e23964680 am: 968eb917aa am: bde98d395a am: 09d21d35f3

Original change: https://android-review.googlesource.com/c/platform/external/mockftpserver/+/1926180

Change-Id: Id3069c09f27a4ef32e8520eaab3992fcbe65e660