Remove Czlib from README

Examples/EchoXcode/README.md

@@ -6,5 +6,5 @@ on the gRPC Xcode project, which requires a local build of the
 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 CzLib, gRPC, CgRPC, and BoringSSL libraries
+then add the gRPC, CgRPC, and BoringSSL libraries
 to the target dependencies of "Echo".