MAINTAINERS: Add entry for samples-request

This is based on discussion with the GA and its simply the people
who have done or tried to do some uploads recently.

Everyone who has a shell account on ffmpeg.org should have powers to
upload samples.

CC: compn <compn@ffmpeg.org>
CC: Thilo Borgmann <thilo.borgmann@mail.de>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit 1a5ed492e577707bc7eb48e25c27a14906adb6d8)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

MAINTAINERS

@@ -56,6 +56,7 @@ presets                             [0]
 metadata subsystem                      Aurelien Jacobs
 release management                      Michael Niedermayer
 API tests                           [0]
+samples-request                     [2] Thilo Borgmann, James Almer, Ben Littler
 
 
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