docs: sysctl/fs: remove references to dquot-max/-nr

dquot-max was removed in 2.4.10.5; dquot-nr was replaced with dqstats
in 2.5.18 which is now /proc/sys/fs/quota. Remove references to
dquot-max and dquot-nr in the sysctl documentation.

Signed-off-by: Stephen Kitt <steve@sk2.org>
Link: https://lore.kernel.org/r/20220930102937.135841-3-steve@sk2.org


Signed-off-by: Jonathan Corbet <corbet@lwn.net>