WebP/Lossy: Add a missing clamp() in `TM_PRED` prediction

The spec has that clamp at the end of
https://datatracker.ietf.org/doc/html/rfc6386#section-12.2:

    The exact algorithm is as follows:
    [...]
               b[r][c] = clamp255(L[r]+ A[c] - P);

For the test images I'm looking at, it doesn't seem to make a
dramatic difference, but omitting it in `B_TM_PRED` did make
a dramatic difference, so add it. (Also, the spec demands it.)

0 files changed, 0 insertions, 0 deletions