[RCD-37] ChangeLog: address PR entries assigned to me
[RCD-37] ChangeLog: address PR entries assigned to me

CDEC-268 was a subtask of CDEC-49 which was included in 1.3 and
already in the changelog.

input-output-hk/pos-haskell-prototype,input-output-hk/cardano-sl,input-output-hk/cardano-sl,input-output-hk/pos-haskell-prototype,input-output-hk/pos-haskell-prototype,input-output-hk/cardano-sl,input-output-hk/cardano-sl