Revert "Nightly: Trigger every 6 hours"

This reverts commit 03557edc98d58181e1f5c1387b22fec8adf0143d.

This has been aligned from the meeting that moves the nightly job as
nightly again as the infra did not reproduce the infinite loop problem
for more than 2 weeks.

Meeting:
TF-M CI Issues review 22nd September

Change-Id: I482efff2b8876e726f519e0bc220d98a19f28366
Signed-off-by: Karl Zhang <karl.zhang@arm.com>
1 file changed