Revert change to cabal version

brittany.cabal

@@ -1,4 +1,3 @@
-cabal-version:        2.2
 name:                 brittany
 version:              0.12.1.1
 synopsis:             Haskell source code formatter
@@ -9,7 +8,7 @@ description: {
   .
   The implementation is documented in more detail <https://github.com/lspitzner/brittany/blob/master/doc/implementation/index.md here>.
 }
-license:              AGPL-3.0-only
+license:              AGPL-3
 license-file:         LICENSE
 author:               Lennart Spitzner
 maintainer:           Lennart Spitzner <hexagoxel@hexagoxel.de>
@@ -17,6 +16,7 @@ copyright:            Copyright (C) 2016-2019 Lennart Spitzner
                       Copyright (C) 2019 PRODA LTD
 category:             Language
 build-type:           Simple
+cabal-version:        1.18
 homepage:             https://github.com/lspitzner/brittany/
 bug-reports:          https://github.com/lspitzner/brittany/issues
 extra-doc-files: {