selftests: net: bump GRO timeout for gro/setup_veth

Commit 51bef03e ("selftests/net: deflake GRO tests") recently
switched to NAPI suspension, and lowered the timeout from 1ms to 100us.
This started causing flakes in netdev-run CI. Let's bump it to 200us.
In a quick test of a debug kernel I see failures with 100us, with 200us
in 5 runs I see 2 completely clean runs and 3 with a single retry
(GRO test will retry up to 5 times).

Reviewed-by: Kevin Krakauer <krakauer@google.com>
Link: https://patch.msgid.link/20250310110821.385621-1-kuba@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>