fix(k2proc): dead code in get_line_spacing_pixels()

[tachibana-shin]

if (allow_text_wrapping)
    if (mlp->median_line_spacing > 0.)
        row_line_spacing_pixels = mlp->median_line_spacing;
    else
        row_line_spacing_pixels = 1.2 * median_single_space_pixels;

when median_line_spacing is zero or negative, the code correctly falls back to 1.2 * median_single_space_pixels instead of silently using an uninitialized/stale value.

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This change is