Fix deprecation warnings (#1430)

Tests/GRPCTests/StreamResponseHandlerRetainCycleTests.swift

@@ -26,7 +26,7 @@ final class StreamResponseHandlerRetainCycleTests: GRPCTestCase {
   var server: Server!
   var client: ClientConnection!
 
-  var echo: Echo_EchoClient!
+  var echo: Echo_EchoNIOClient!
 
   override func setUp() {
     super.setUp()
@@ -42,7 +42,7 @@ final class StreamResponseHandlerRetainCycleTests: GRPCTestCase {
       .withBackgroundActivityLogger(self.clientLogger)
       .connect(host: "localhost", port: self.server.channel.localAddress!.port!)
 
-    self.echo = Echo_EchoClient(
+    self.echo = Echo_EchoNIOClient(
       channel: self.client,
       defaultCallOptions: CallOptions(logger: self.clientLogger)
     )

Tests/GRPCTests/WithConnectedSocketTests.swift

@@ -62,7 +62,7 @@ class WithConnectedSockettests: GRPCTestCase {
       XCTAssertNoThrow(try connection.close().wait())
     }
 
-    let client = Echo_EchoClient(channel: connection)
+    let client = Echo_EchoNIOClient(channel: connection)
     let resp = try client.get(Echo_EchoRequest(text: "Hello")).response.wait()
     XCTAssertEqual(resp.text, "Swift echo get: Hello")
   }