update `source-repository` location
The source repository on Hackage (https://hackage.haskell.org/package/hpc) is currently:
Source repo head: git clone http://git.haskell.org/packages/hpc.git
The source repository on Hackage (https://hackage.haskell.org/package/hpc) is currently:
Source repo head: git clone http://git.haskell.org/packages/hpc.git