mon: correct typo in command desc

in 46586b22, we introduced the "osd pool application get" command, but
in this command's desc field, we had a typo: "req=fasle". this didn't
cause any issue, because we always consider "true" or "True" as true,
and false otherwise when formatting a command desc into JSON.

but it's still not correct. let's fix this typo.

Fixes: https://tracker.ceph.com/issues/77251
Signed-off-by: Kefu Chai <k.chai@proxmox.com>