remove boost 1.70 mention about Boost::headers

Author: NeroBurner

docs/packages/pkg/Boost.rst

@@ -5,8 +5,6 @@
 Boost
 =====
 
-Since boost 1.70 you should use for header only libraries as target:
-
 .. code-block:: cmake
 
     # Header-only libraries

examples/Boost/CMakeLists.txt

@@ -15,7 +15,7 @@ hunter_add_package(Boost)
 find_package(Boost CONFIG REQUIRED)
 
 add_executable(foo foo.cpp)
-target_link_libraries(foo PUBLIC Boost::headers) # Since boost 1.70 you should use Boost::headers as target
+target_link_libraries(foo PUBLIC Boost::headers)
 
 set(project_license "${CMAKE_CURRENT_BINARY_DIR}/LICENSE.txt")
 file(