quota: extend quota for dataset

This patch relax the quota limitation for dataset by around 3%.
What this means is that user can write more data then the quota is
set to. However thanks to that we can get more stable bandwidth, in
case when we are overwriting data in-place, and not consuming any
additional space.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Allan Jude <allan@klarasystems.com>
Signed-off-by: Mariusz Zaborski <oshogbo@vexillium.org>
Sponsored-by: Zededa Inc.
Sponsored-by: Klara Inc.
Closes #13839