Visibility field not listed under cabal spec changes.

[merijn]

The cabal docs list the visibility field as existing as of Cabal 3.0, however the list of format changes doesn't list it as an addition in 3.0

[23Skidoo]

/cc @fgaz

[jneira]

visibility is not included anymore in the linked page above: https://cabal.readthedocs.io/en/latest/developing-packages.html#pkg-field-library-visibility
I guess it still was added in 3.0 and should be included in cabal format changes