WebPParseHeaders: remove obsolete animation TODO
WebPParseHeaders: remove obsolete animation TODO

The WebPDemux and WebPAnimDecoder APIs are provided for the purpose of
animated webp parsing and decoding. No major changes are currently
planned for the libwebp API.

Change-Id: I2758ecda195b0c4091572d5731a0a85fa3716303

webmproject/libwebp,PKRoma/libwebp,PKRoma/libwebp,webmproject/libwebp,webmproject/libwebp,PKRoma/libwebp,PKRoma/libwebp,PKRoma/libwebp,PKRoma/libwebp,webmproject/libwebp,webmproject/libwebp