Point zcash-light-client-ffi to corresponding feature branch

Package.resolved

@@ -86,9 +86,9 @@
         "package": "libzcashlc",
         "repositoryURL": "https://github.com/zcash-hackworks/zcash-light-client-ffi.git",
         "state": {
-          "branch": null,
-          "revision": "b7e8a2abab84c44046b4afe4ee4522a0fa2fcc7f",
-          "version": "0.0.3"
+          "branch": "librustzcash_0_7",
+          "revision": "127a6b9d19841fea232bf0d0887ae5f2cad8df04",
+          "version": null
         }
       }
     ]

Package.swift

@@ -16,7 +16,7 @@ let package = Package(
     dependencies: [
         .package(url: "https://github.com/grpc/grpc-swift.git", from: "1.8.0"),
         .package(url: "https://github.com/stephencelis/SQLite.swift.git", from: "0.13.0"),
-        .package(name:"libzcashlc", url: "https://github.com/zcash-hackworks/zcash-light-client-ffi.git", from: "0.0.3"),
+        .package(name:"libzcashlc", url: "https://github.com/zcash-hackworks/zcash-light-client-ffi.git", branch: "librustzcash_0_7"),
     ],
     targets: [
         .target(