Set uppoer bound on aeson

Otherwise the build fails with:

[ 1 of 16] Compiling JsonRpc          ( src/JsonRpc.hs, dist/build/chainweb-mining-client/chainweb-mining-client-tmp/JsonRpc.o, dist/build/chainweb-mining-client/chainweb-mining-client-tmp/JsonRpc.dyn_o )

src/JsonRpc.hs:162:22: error:
    • Expecting one more argument to ‘A.KeyValue kv’
      Expected a constraint,
        but ‘A.KeyValue kv’ has kind ‘* -> Constraint’
    • In the type signature:
        requestProperties :: A.KeyValue kv =>
                             A.ToJSON a => T.Text -> a -> Maybe MsgId -> [kv]
    |
162 | requestProperties :: A.KeyValue kv => A.ToJSON a => T.Text -> a -> Maybe MsgId -> [kv]
    |                      ^^^^^^^^^^^^^

chainweb-mining-client.cabal

@@ -72,7 +72,7 @@ executable chainweb-mining-client
           attoparsec >=0.14
         , base >=4.10 && <5
         , base16-bytestring >=1.0
-        , aeson >=1.5
+        , aeson >=1.5 && <2
         , async >=2.2
         , bytes >=0.17
         , bytestring >=0.10