Help: Fix classification of load_command in command TOC.

In CMake 3.0, the load_command command was deprecated.  However, the
position of load_command in the help TOC was not fixed at that time:
it was still listed as a "Normal Command".

Help/manual/cmake-commands.7.rst

@@ -71,7 +71,6 @@ These commands may be used freely in CMake projects.
    /command/link_libraries
    /command/list
    /command/load_cache
-   /command/load_command
    /command/macro
    /command/mark_as_advanced
    /command/math
@@ -119,6 +118,7 @@ versions of CMake.  Do not use them in new code.
    /command/install_files
    /command/install_programs
    /command/install_targets
+   /command/load_command
    /command/make_directory
    /command/output_required_files
    /command/remove