makeFixedOutputPath(): Drop superfluous HashType argument

perl/lib/Nix/Store.xs

src/libexpr/primops.cc

src/libstore/binary-cache-store.cc

src/libstore/build.cc

src/libstore/derivations.cc

src/libstore/derivations.hh

src/libstore/download.cc

src/libstore/local-store.cc

src/libstore/store-api.cc

src/libstore/store-api.hh

src/nix-prefetch-url/nix-prefetch-url.cc

src/nix-store/nix-store.cc