Allow aeson 2.1

Builds fine and all tests pass.

README.md

@@ -1,11 +1,4 @@
 # brittany [![Hackage version](https://img.shields.io/hackage/v/brittany.svg?label=Hackage)](https://hackage.haskell.org/package/brittany) [![Stackage version](https://www.stackage.org/package/brittany/badge/lts?label=Stackage)](https://www.stackage.org/package/brittany) [![Build Status](https://secure.travis-ci.org/lspitzner/brittany.svg?branch=master)](http://travis-ci.org/lspitzner/brittany)
-
-:warning:
-This project is effectively unmaintained!
-I ([@tfausak](https://github.com/tfausak)) would recommend switching to another formatter.
-At time of writing (2022-11-11), I would suggest [Ormolu](https://github.com/tweag/ormolu).
-Or if you prefer some configuration, I would suggest [Fourmolu](https://github.com/fourmolu/fourmolu).
-
 haskell source code formatter
 
 ![Output sample](https://github.com/lspitzner/brittany/raw/master/brittany-sample.gif)

brittany.cabal

@@ -38,7 +38,7 @@ flag pedantic
 
 common library
   build-depends:
-    , aeson ^>= 2.0.1
+    , aeson ^>= 2.0.1 || ^>= 2.1
     , base ^>= 4.15.0
     , butcher ^>= 1.3.3
     , bytestring ^>= 0.10.12