[DEVOPS-957] AppVeyor: Update Rocksdb.zip URL to S3 location
[DEVOPS-957] AppVeyor: Update Rocksdb.zip URL to S3 location

AppVeyor are deleting old build artifacts.

(cherry picked from commit 39d4d18163c8faab4e04b95ffa3c9a8737ae3d1a)

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