Doc: Update the \modulestate command

There are different states that a module can be in, for example, an
'active' state, a deprecated state, marked for deprecation, or a custom
state that the user can define.

Whilst the \modulestate command can be used with an argument, for
example, deprecated, QDoc will not actually deprecate the module. It
will just generate a sentence on the module page. This can cause confusion
for the user.

This patch expands on the \modulestate command and explains that it can be
used for custom module state descriptions. A note was added to state
that it should not be used to actually deprecate a module.

Fixes: QTBUG-133739
Change-Id: I4d439a59d6f4fbee4506ea2a297df107853992da
Reviewed-by: Topi Reiniö <topi.reinio@qt.io>
Reviewed-by: Andreas Eliasson <andreas.eliasson@qt.io>
(cherry picked from commit 78be281374fcc6959f4d386ec7b08d1cc90c0422)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
(cherry picked from commit 2f05f79763365aed12a0522f32079827efca40e4)

src/qdoc/qdoc/doc/qdoc-manual-contextcmds.qdoc

@@ -436,11 +436,10 @@
     \target modulestate-command
     \section1 \\modulestate
 
-    The \\modulestate command can be used within a \\module or \\qmlmodule
-    topic to provide a module state description other than \e preliminary or
-    \e deprecated.
+    Use the \\modulestate command within a \\module or \\qmlmodule
+    topic to provide a custom module state description.
 
-    Rest of the line is taken as an argument that describes the module's
+    The command takes an argument that describes the module's
     state. For example:
 
     \badcode *
@@ -456,6 +455,9 @@
     This module is in \e {Technical Preview} state.
     \endquotation
 
+    \note Do not use this command to deprecate a module. Use the
+    \l {deprecated-command}{\\deprecated} instead.
+
     In HTML output, this state information appears also in the navigation
     bar (breadcrumbs) of reference pages for the module's members.