Fix incorrect UUID for hello world TA

With the recently fixed UUID changes (commit in optee_os:
(9a8a19cdba48dbca89c2a35d7984e9ec28f97bda) we missed to fix the hello
world TA.

Signed-off-by: Joakim Bech <joakim.bech@linaro.org>
Reviewed-by: Jens Wiklander <jens.wiklander@linaro.org>
Reviewed-by: Igor Opaniuk <igor.opaniuk@linaro.org>