Remove unused files in .gitlab

These were left over after 6078b429

.gitlab/gen-ci.cabal

-cabal-version: 3.0
-name:          gen-ci
-version:       0.1.0.0
-build-type:    Simple
-
-common warnings
-  ghc-options: -Wall
-
-executable gen_ci
-  import:           warnings
-  main-is:          gen_ci.hs
-  build-depends:
-    , aeson       >=1.8.1
-    , base
-    , bytestring
-    , containers
-
-  default-language: Haskell2010

.gitlab/hie.yaml

-cradle:
-  cabal: