requirements.txt: change package name "hub" to "git-spindle"
requirements.txt: change package name "hub" to "git-spindle"

Package "hub" has been renamed some time ago to "git-spindle".
Recently package with the same name "hub" has been released on PyPi
page, which causes installing pip requirements.txt to fail since
it is trying to install different package.

Signed-off-by: Marcin Sloniewski <ab0747760c36c1a2985131c8564aac2c7096b8c3@gmail.com>

nashif/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,finikorg/zephyr,Vudentz/zephyr,galak/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,Vudentz/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,finikorg/zephyr,nashif/zephyr,galak/zephyr,nashif/zephyr,Vudentz/zephyr,galak/zephyr,nashif/zephyr,galak/zephyr,nashif/zephyr