Bump haddock submodule on HEAD
The ghc-head branch of haddock is still on version 2.28.0, while 9.8 is on 2.30.0. We should merge ghc-head with at least the newest haddock version on release branches.
The ghc-head branch of haddock is still on version 2.28.0, while 9.8 is on 2.30.0. We should merge ghc-head with at least the newest haddock version on release branches.