Bump version to 1.2.0

Current version says `1.1.3` but that should never be released to
CHaP because it depends on `crypton` instead of `crypton` and this
changes causes a bunch of breakage downstream.

Author: erikd

cardano-crypto.cabal

@@ -1,5 +1,5 @@
 name:                cardano-crypto
-version:             1.1.3
+version:             1.2.0
 synopsis:            Cryptography primitives for cardano
 description:
 homepage:            https://github.com/input-output-hk/cardano-crypto#readme