Add brick to horizon.dhall on lts/ghc-9.8.x
Follow-up to !207 (merged). brick was listed in requiredPackages on 9.8.x but never actually declared in horizon.dhall (only branch where this was the case). This caused horizon-platform 9.8.x's cursor-brick package to fail evaluation when it tried to find brick via legacyPackages. This MR adds brick + its transitive deps (vty-crossplatform, vty-unix) so brick is real on 9.8.x.