tests: kernel: timer: starve: Add proper timeout value
tests: kernel: timer: starve: Add proper timeout value

The test in its default configuration needs 3600 seconds to complete,
so use such timeout value in testcase.yaml so that twister called with
--enable-slow option can successfully execute it.

Signed-off-by: Andrzej Głąbek <6788b8d556a8a447102338fc996c42180ecff44e@nordicsemi.no>

zephyrproject-rtos/zephyr,galak/zephyr,galak/zephyr,galak/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr