zfs-module-parameters.5: remove nonexistent parameters

zfs_arc_overflow_shift was never a parameter:
ca0bf58d65f77e944b9905571df9a2eae647aeca ("Illumos 5497 - lock
contention on arcs_mtx") is the only result in
git log -Soverflow_shift, and it wasn't exposed then, nor is it now

zfs_read_chunk_size was renamed to zfs_vnops_read_chunk_size in
e53d678d4ad596a310d51dab107bb6fa97e2b226 ("Share zfs_fsync, zfs_read,
zfs_write, et al between Linux and FreeBSD")

zio_decompress_fail_fraction was never a parameter: it was added in
c3bd3fb4ac49705819666055ff1206a9fa3d1b9e ("OpenZFS 9403 - assertion
failed in arc_buf_destroy()") as a developer aid for setting in zdb, but
it's a dangerous test tunable and has no place in public documentation,
(not to mention that it obviously doesn't work):

Although this did uncover a few low priority issues, this

unfortuantely also causes ztest to ASSERT in many locations where the
code is working correctly since it is designed to fail on IO errors.
Developers can manually set this variable with the '-o' option to find
and debug issues.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Richard Laager <rlaager@wiktel.com>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Closes #12157