main/lynx: remove gzip dependency

Grepped the Lynx v2.9.2 codebase for gzip usage, and the only flags used were -9, -d and -n as far as I could tell, all of which busybox gzip supports. Saving of timestamp is already disabled in busybox's gzip, so the -n flag is quietly ignored. Overriding gzip with busybox's, I was still able to open and read through gzipped sites. I think it's safe to strip the gzip dependency.