webp,cmake: Remove unnecessary include dirs
webp,cmake: Remove unnecessary include dirs

Following crrev.com/c/webm/libwebp/+/3038647

Change-Id: Id43ed9b1cc02a7333bc64e82523122f483c9350a

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