kate: remove invalid clean

palette doesn't need to be freed since it's stack allocated.

Signed-off-by: Hugo Beauzée-Luyssen <hugo@beauzee.fr>
(cherry picked from commit 73f7b186)
Signed-off-by: Hugo Beauzée-Luyssen <hugo@beauzee.fr>

modules/codec/kate.c

@@ -1169,7 +1169,6 @@ static subpicture_t *SetupSimpleKateSPU( decoder_t *p_dec, subpicture_t *p_spu,
         CreateKatePalette( fmt.p_palette, ev->palette );
 
         p_bitmap_region = subpicture_region_New( &fmt );
-        video_format_Clean( &fmt );
         if( !p_bitmap_region )
         {
             msg_Err( p_dec, "cannot allocate SPU region" );