Fix Readme installation instructions

Removes manually adding the include directory from the Readme install instructions. The manual step is not needed since the include dir is already added on the library target by the current CMake configuration.

Author: franklange

README.md

@@ -103,10 +103,6 @@ Example for Linux:
 ```cmake
 add_subdirectory(${CMAKE_CURRENT_LIST_DIR}/thirdparty/SQLiteCpp)
 
-include_directories(
-  ${CMAKE_CURRENT_LIST_DIR}/thirdparty/SQLiteCpp/include
-)
-
 add_executable(main src/main.cpp)
 target_link_libraries(main
   SQLiteCpp