[examples]: removed hyphens

Replaced hyphens with underscores in examples
project definition for all examples which had
hyphens in their project name. dpp-enrollee is
an exceptions because the name matches the
project directory name while the project
directory also contains hyphens.

examples/get-started/hello_world/CMakeLists.txt

@@ -3,4 +3,4 @@
 cmake_minimum_required(VERSION 3.5)
 
 include($ENV{IDF_PATH}/tools/cmake/project.cmake)
-project(hello-world)
+project(hello_world)

examples/get-started/hello_world/Makefile

@@ -3,6 +3,6 @@
 # project subdirectory.
 #
 
-PROJECT_NAME := hello-world
+PROJECT_NAME := hello_world
 
 include $(IDF_PATH)/make/project.mk