libctf: fix a comment typo

ctf_dedup's intern() function does not return a dynamically allocated
string, so I just spent ten minutes auditing for obvious memory leaks
that couldn't actually happen.  Update the comment to note what it
actually returns (a pointer into an atoms table: i.e. possibly not
a new string, and not so easily leakable).

libctf/
	* ctf-dedup.c (intern): Update comment.

libctf/ctf-dedup.c

@@ -412,7 +412,7 @@ intern (ctf_dict_t *fp, char *atom)
 /* Add an indication of the namespace to a type name in a way that is not valid
    for C identifiers.  Used to maintain hashes of type names to other things
    while allowing for the four C namespaces (normal, struct, union, enum).
-   Return a new dynamically-allocated string.  */
+   Return a pointer into the cd_decorated_names atoms table.  */
 static const char *
 ctf_decorate_type_name (ctf_dict_t *fp, const char *name, int kind)
 {