Fix index entry for comment-indent-function.

man/programs.texi

@@ -1062,7 +1062,7 @@ inserting a terminator on the old line, and not inserting a starter on
 the new line.  In languages where multi-line comments work, the choice
 of value for this variable is a matter of taste.
 
-@vindex comment-indent-function
+@cindex @code{comment-indent-function} property
   The variable @code{comment-indent-function} should contain a function
 that will be called to compute the indentation for a newly inserted
 comment or for aligning an existing comment.  It is set differently by