Remove deprecation warning
Remove deprecation warning

This warning is making CI logs difficult to read and the work to
address the warning is way out of the scope of this PR, so silencing
for now.

Credit to Jessica for this suggestion, original commit: https://github.com/alphagov/whitehall/pull/6169/commits/2f1128e8561237d047627f1f2406a19196dfa96d

alphagov/whitehall,alphagov/whitehall,alphagov/whitehall,alphagov/whitehall