Your raid is already in recovery. In about 10 hours the process will be finished and status should return to normal.
If you wish to visualize the proces you can do watch -n 0,1 cat /proc/mdstat where 0,1 stands for 0,1sec
To see detail status of the raid use mdadm --detail /dev/mdxxx where xxx stands for 126, 127 or other raid
Here are some commands you can try if the raid doesn’t readd the disk automatically (but be carefull, please read the man-pages of mdadm!):
set disk faulty:
mdadm --manage --set-faulty /dev/mdxxx /dev/sdnx
remove disk:
mdadm --manage /dev/mdxxx -r /dev/sdnx
readd disk:
mdadm --manage /dev/mdxxx -a /dev/sdnx
sdnx stands for the disk to readd like sdb1 or sda2 …
Some times a reboot is required AFAICR.