Revert "Export versioned targets for CMake"

This reverts commit 382bf3de06.

Revert PR #110
https://github.com/KhronosGroup/Vulkan-Headers/pull/110

cmake/Config.cmake.in

@@ -1,25 +0,0 @@
-@PACKAGE_INIT@
-
-include("${CMAKE_CURRENT_LIST_DIR}/@TARGETS_EXPORT_NAME@.cmake")
-check_required_components("@PROJECT_NAME@")
-
-# ALIAS for imported target requires CMake >= 3.11:
-# - https://cmake.org/cmake/help/latest/release/3.11.html#other
-if(NOT CMAKE_VERSION VERSION_LESS 3.11)
-    if(NOT TARGET Vulkan::Headers)
-        set_target_properties(
-            Vulkan::Vulkan-Headers
-            PROPERTIES
-            IMPORTED_GLOBAL True
-        )
-        add_library(Vulkan::Headers ALIAS Vulkan::Vulkan-Headers)
-      endif()
-      if(NOT TARGET Vulkan::Registry)
-        set_target_properties(
-            Vulkan::Vulkan-Registry
-            PROPERTIES
-            IMPORTED_GLOBAL True
-        )
-        add_library(Vulkan::Registry ALIAS Vulkan::Vulkan-Registry)
-    endif()
-endif()