debugupgraderepo: minor documentation fix
When we specify `--no-changelog --no-manifest --no-filelog` we skip all revlog
optimization instead of all filelog optimization.
Also while I was here, for consistency, I did `optimisation` -> `optimization`
to make it consistent with rest of occurrences.
Note: I am not native speaker and I only changed it because of consistency. I
don't know which one is correct.
Differential Revision: https://phab.mercurial-scm.org/D9617
edition = "2018"
max_width = 79
wrap_comments = true
error_on_line_overflow = true