refactor(docs): rename dependency group to docs

The dependency group for documentation has been renamed to docs [1],
rename it to align with this change.

[1] https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/30344

Signed-off-by: Harrison Mutai <harrison.mutai@arm.com>
Change-Id: Ia29170b4416aa9a3466444f129d453872a5e482b
1 file changed