Inconsistent indexing fig. on page 498 and text on page 499

[olivertomic]

The indexing for the discrete convolution example in the figure of page 498 starts with 1 (that is y[1], y[2], y[3]) whereas the example in the text on page 499 (second section of chapter The effect of zero-padding in a convolution starts at index 0 (that is y[0], etc.). If we were to use Python indexing, the index in the figure should be decreased by 1, I guess.