docs: user/supported_devices: remove unreferenced footnote

Sphinx 8.1 now warns about unreferend footnotes, breaking our CI.

docs/user/supported_devices.rst

@@ -574,12 +574,6 @@ See also: :doc:`x86`
 Footnotes
 ---------
 
-.. [#device-class-tiny]
-  These devices only support a subset of Gluons capabilities due to flash or memory
-  size constraints. Devices are classified as tiny if they provide less than 7M of usable
-  flash space or have a low amount of system memory. For more information, see the
-  developer documentation: :ref:`device-class-definition`.
-
 .. [#avmflash]
   For instructions on how to flash AVM devices, visit https://fritz-tools.readthedocs.io