docs: update tooling

Update Sphinx and dependencies to a newer version.

This is to solve set-up issues due to non-pinned dependencies updated to
an incompatible version.

Change-Id: Idbecfdba4b701b68654a575179930bce09e0b804
Signed-off-by: Gyorgy Szing <gyorgy.szing@arm.com>
1 file changed