input: docs: properly format ToC headings

"class:: toc-title" was a workaround for older Sphinx versions that are
no longer supported.

The canonical way to add a heading to the ToC is to use :caption:.
Do that.

Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: linux-input@vger.kernel.org
Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20231027081830.195056-8-vegard.nossum@oracle.com

Documentation/input/input_kapi.rst

@@ -4,11 +4,8 @@
 Linux Input Subsystem kernel API
 ################################
 
-.. class:: toc-title
-
-        Table of Contents
-
 .. toctree::
+   :caption: Table of Contents
    :maxdepth: 2
    :numbered:
 

Documentation/input/input_uapi.rst

@@ -4,11 +4,8 @@
 Linux Input Subsystem userspace API
 ###################################
 
-.. class:: toc-title
-
-        Table of Contents
-
 .. toctree::
+   :caption: Table of Contents
    :maxdepth: 2
    :numbered:
 

Documentation/input/joydev/index.rst

@@ -6,11 +6,8 @@ Linux Joystick support
 
 :Copyright: |copy| 1996-2000 Vojtech Pavlik <vojtech@ucw.cz> - Sponsored by SuSE
 
-.. class:: toc-title
-
-	Table of Contents
-
 .. toctree::
+	:caption: Table of Contents
 	:maxdepth: 3
 
 	joystick