tf-m-nightly-code-coverage: Disable nightly trigger (resubmit)

The CC job keeps failing these days and occupies too many CI resources.
Disable the nightly trigger to save resources.

Resubmitted because previous attempt wasn't processed correctly.

Signed-off-by: Xinyu Zhang <xinyu.zhang@arm.com>
Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
Change-Id: I7607e99d8c0b1f765e931b2de3f055b58e1de837
1 file changed