Kopia maintenance cannot choose quick

I was hoping to run quick maintenance, but it looks like it ignores the option.

root:# ./kopia maintenance run --no-full
Running full maintenance…
Looking for active contents…
Looking for unreferenced contents…

this was using 20220723.0.152313 build: 0e62d64576d58c653bc79b709c4a8ad071e701bb from: kopia/kopia

Full is the only mode now for recent repositories. Quick maintenance only made sense for legacy formats.

We should probably hide this flag.