[adjacent.difference] Use code font for *i expression.

Fixes #287

Author: jwakely

source/numerics.tex

@@ -8797,7 +8797,7 @@
 value type, initializes it with \tcode{*first},
 and assigns the result to \tcode{*result}. For every iterator \tcode{i} in \range{first + 1}{last}
 in order, creates an object \tcode{val} whose type is \tcode{InputIterator}'s value type, initializes it
-with *i, computes \tcode{val - acc} or \tcode{binary_op(val, acc)}, assigns the result
+with \tcode{*i}, computes \tcode{val - acc} or \tcode{binary_op(val, acc)}, assigns the result
 to \tcode{*(result + (i - first))}, and move assigns from \tcode{val} to \tcode{acc}.
 
 \pnum