Remove `reboot emergency`.

This isn't in the bootloader requirements doc, and the internet implies
that you actually need to use `fastboot oem edl` or `fastboot oem
reboot-edl` anyway.

Bug: N/A
Test: N/A
Change-Id: I0b7cd9839fbd06fc104d029e92d5986dc3c6eda3
1 file changed