DOCS/vo: remove some dated deprecation warnings about --vo=rpi

Very amusingly, the manual previously said "The rpi VO will be removed
in mpv 0.23.0." Obviously, this didn't happen. It looks like wm4 changed
his mind on this with 51fd8f6fe1, but
never updated the docs. What was the problem? Who knows but allegedly
there are people that use --vo=rpi (it's supposed to work at least).
Actually context_rpi is probably broken since wm4 changed fullscreen
handling in 59cdfe50b2 and no one ever
bothered to fix it after that commit. In fact, that's the last commit
that touched that particular file. Someone did actually fix vo_rpi after
that so that one probably works at least. Anyways, I wouldn't mind just
deleting all rpi stuff, but there's probably some people out there that
use it so whatever. Remove the outdated deprecated language in the
documentation and just accept that we support this unfortunately.

DOCS/man/vo.rst

@@ -569,14 +569,7 @@ Available video output drivers are:
 ``rpi`` (Raspberry Pi)
     Native video output on the Raspberry Pi using the MMAL API.
 
-    This is deprecated. Use ``--vo=gpu`` instead, which is the default and
-    provides the same functionality. The ``rpi`` VO will be removed in
-    mpv 0.23.0. Its functionality was folded into --vo=gpu, which now uses
-    RPI hardware decoding by treating it as a hardware overlay (without applying
-    GL filtering). Also to be changed in 0.23.0: the --fs flag will be reset to
-    "no" by default (like on the other platforms).
-
-    The following deprecated global options are supported by this video output:
+    The following global options are supported by this video output:
 
     ``--rpi-display=<number>``
         Select the display number on which the video overlay should be shown