Help: Fix location of install() note about superseded commands

The note regarding commands superseded by install() somehow wound
up nested under the install(EXPORT) signature, when it has nothing
to do with install(EXPORT). Move it to the top level, immediately
before the Examples section.

Help/command/install.rst

@@ -898,16 +898,6 @@ Signatures
   executable from the installation tree using the imported target name
   ``mp_myexe`` as if the target were built in its own tree.
 
-  .. note::
-    This command supersedes the :command:`install_targets` command and
-    the :prop_tgt:`PRE_INSTALL_SCRIPT` and :prop_tgt:`POST_INSTALL_SCRIPT`
-    target properties.  It also replaces the ``FILES`` forms of the
-    :command:`install_files` and :command:`install_programs` commands.
-    The processing order of these install rules relative to
-    those generated by :command:`install_targets`,
-    :command:`install_files`, and :command:`install_programs` commands
-    is not defined.
-
 .. signature::
   install(RUNTIME_DEPENDENCY_SET <set-name> [...])
 
@@ -971,6 +961,16 @@ Signatures
   * ``POST_INCLUDE_FILES <file>...``
   * ``POST_EXCLUDE_FILES <file>...``
 
+.. note::
+  This command supersedes the :command:`install_targets` command and
+  the :prop_tgt:`PRE_INSTALL_SCRIPT` and :prop_tgt:`POST_INSTALL_SCRIPT`
+  target properties.  It also replaces the ``FILES`` forms of the
+  :command:`install_files` and :command:`install_programs` commands.
+  The processing order of these install rules relative to
+  those generated by :command:`install_targets`,
+  :command:`install_files`, and :command:`install_programs` commands
+  is not defined.
+
 Examples
 ^^^^^^^^