rename createTransportChannel to getTransportChannel

Change-Id: I65972734a494cbf5cece251edfb871d493a48d1c

Author: nicholsl

google-cloud-bigtable/src/main/java/com/google/cloud/bigtable/gaxx/grpc/BigtableTransportChannelProvider.java

@@ -103,10 +103,6 @@ public TransportChannelProvider withPoolSize(int size) {
 
   @Override
   public TransportChannel getTransportChannel() throws IOException {
-    return createTransportChannel();
-  }
-
-  private TransportChannel createTransportChannel() throws IOException {
     // This provider's main purpose is to replace the default GAX ChannelPool
     // with a custom BigtableChannelPool, reusing the delegate's configuration.