Tweak Echo Readme (see #273)

Examples/EchoXcode/README.md

@@ -7,4 +7,4 @@ gRPC Core C library. To build that, please run "make" in the
 root of your gRPC distribution. Next use Xcode's "Add Files..."
 command to add the SwiftGRPC.xcodeproj to your project and
 then add the gRPC, CgRPC, BoringSSL, and SwiftProtobuf
-libraries to the target dependencies of "Echo".
+libraries to the "Linked Frameworks and Libraries" build phase of "Echo".