Remove GetThreadSuffixSupported from GDBRemoteCommunication **base** class

Despite its comment, the function is only used in the Client class, and its presence was merely
complicating mock implementation in unit tests.

llvm-svn: 278785
diff --git a/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationClient.h b/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationClient.h
index 424a949..83502f4 100644
--- a/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationClient.h
+++ b/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationClient.h
@@ -65,7 +65,7 @@
                                         std::string &response_string);
 
     bool
-    GetThreadSuffixSupported () override;
+    GetThreadSuffixSupported();
 
     // This packet is usually sent first and the boolean return value
     // indicates if the packet was send and any response was received