[alg.copy] Add missing \tcode formatting

Author: jensmaurer

source/algorithms.tex

@@ -4615,7 +4615,7 @@
 into the range \range{result - $N$}{result}
 starting from \tcode{last - 1} and proceeding to \tcode{first}.
 \begin{footnote}
-\tcode{copy_backward} can be used instead of copy
+\tcode{copy_backward} can be used instead of \tcode{copy}
 when \tcode{last} is in the range \range{result - $N$}{result}.
 \end{footnote}
 For each positive integer $n \le N$,