avcodec/vdpau_hevc: Remove experimental flag

The latest nvidia 355.06 drivers fixes the interleaving bug when
video surfaces are rendered. It still seems to be broken for
read-back with getBits but that's sufficiently uninteresting that
I don't think we need to wait for it to remove the flag.

libavcodec/vdpau_hevc.c

@@ -427,7 +427,6 @@ AVHWAccel ff_hevc_vdpau_hwaccel = {
     .type           = AVMEDIA_TYPE_VIDEO,
     .id             = AV_CODEC_ID_HEVC,
     .pix_fmt        = AV_PIX_FMT_VDPAU,
-    .capabilities   = HWACCEL_CODEC_CAP_EXPERIMENTAL,
     .start_frame    = vdpau_hevc_start_frame,
     .end_frame      = vdpau_hevc_end_frame,
     .decode_slice   = vdpau_hevc_decode_slice,