Documentation: gpu/drm-uapi: eliminate duplicated word

Drop the doubled word "when".

Signed-off-by: Randy Dunlap <[e-mail]>
Cc: Jonathan Corbet <[e-mail]>
Cc: [e-mail]
Cc: David Airlie <[e-mail]>
Cc: Daniel Vetter <[e-mail]>
Cc: [e-mail]
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jonathan Corbet <[e-mail]>

Documentation/gpu/drm-uapi.rst

···
 EPERM/EACCES:
         Returned for an operation that is valid, but needs more privileges.
         E.g. root-only or much more common, DRM master-only operations return
-        this when when called by unpriviledged clients. There's no clear
+        this when called by unpriviledged clients. There's no clear
         difference between EACCES and EPERM.
 
 ENODEV: