ci: PULL_REQUEST is reserved, use something else
ci: PULL_REQUEST is reserved, use something else

Use PULL_REQUEST_NR instead of PULL_REQUEST which is reserved by
shippable.

Signed-off-by: Anas Nashif <0d9952ec84ac43c159f6b7e7ed99a9080c00dd6e@intel.com>

GiulianoFranchetto/zephyr,finikorg/zephyr,GiulianoFranchetto/zephyr,nashif/zephyr,punitvara/zephyr,ldts/zephyr,GiulianoFranchetto/zephyr,finikorg/zephyr,explora26/zephyr,ldts/zephyr,nashif/zephyr,Vudentz/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,ldts/zephyr,Vudentz/zephyr,Vudentz/zephyr,GiulianoFranchetto/zephyr,nashif/zephyr,nashif/zephyr,galak/zephyr,explora26/zephyr,GiulianoFranchetto/zephyr,explora26/zephyr,punitvara/zephyr,explora26/zephyr,ldts/zephyr,Vudentz/zephyr,punitvara/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,punitvara/zephyr,nashif/zephyr,finikorg/zephyr,punitvara/zephyr,finikorg/zephyr,ldts/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,explora26/zephyr,Vudentz/zephyr