svt-av1: remove BSD-2 from licenses
svt-av1: remove BSD-2 from licenses

Quoting from the README:

> Up to v0.8.7, SVT-AV1 is licensed under the BSD-2-clause license and
> the Alliance for Open Media Patent License 1.0. See LICENSE and
> PATENTS for details. Starting from v0.9, SVT-AV1 is licensed under
> the BSD-3-clause clear license and the Alliance for Open Media
> Patent License 1.0. See LICENSE and PATENTS for details.

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