Removed unnecessary include call in install/

`include("${PROJECT_SOURCE_DIR}/cmake/helper.cmake")` is called in
project root CMakeLists.txt, so it is not necessary to have it in
`install/` as well.

Author: jfdev001

install/CMakeLists.txt

@@ -1,5 +1,3 @@
-# Get the macros and functions we'll need
-include("${PROJECT_SOURCE_DIR}/cmake/helper.cmake")
 include(CMakePackageConfigHelpers)
 
 # Install the library and necessary include files
@@ -50,4 +48,4 @@ configure_file(
 install(
   FILES ${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}.pc
   DESTINATION ${CMAKE_INSTALL_LIBDIR}/pkgconfig
-)
+)