clean up mqtt5 x509 sample and readme

Author: xiazhvera

samples/mqtt5/mqtt5_pubsub/CMakeLists.txt

@@ -1,11 +1,9 @@
 cmake_minimum_required(VERSION 3.9...3.31)
 # note: cxx-17 requires cmake 3.8, cxx-20 requires cmake 3.12
-project(mqtt5_pubsub CXX)
+project(mqtt5_x509 CXX)
 
 file(GLOB SRC_FILES
        "*.cpp"
-       "../../utils/CommandLineUtils.cpp"
-       "../../utils/CommandLineUtils.h"
 )
 
 add_executable(${PROJECT_NAME} ${SRC_FILES})