tree-walk.h: fix incorrect API comment

When commit 50ddb08 (tree-walk.c: remove the_repo from
get_tree_entry(), 2019-06-27) added an extra parameter to
get_tree_entry(), it did not fix the ordering comment about the meaning
of the parameters.  Rather than just changing "third"->"fourth" and
"fourth"->"fifth", give the paramemters meaningful names (or actually,
just take the existing names from the get_tree_entry() definition in the
tree-walk.c file) and strike the comment.

Signed-off-by: Elijah Newren <[email protected]>

Author: newren

tree-walk.h

@@ -177,10 +177,11 @@ struct traverse_info {
 
 /**
  * Find an entry in a tree given a pathname and the sha1 of a tree to
- * search. Returns 0 if the entry is found and -1 otherwise. The third
- * and fourth parameters are set to the entry's sha1 and mode respectively.
+ * search. Returns 0 if the entry is found and -1 otherwise.
  */
-int get_tree_entry(struct repository *, const struct object_id *, const char *, struct object_id *, unsigned short *);
+int get_tree_entry(struct repository *repo, const struct object_id *tree_oid,
+		   const char *name, struct object_id *oid,
+		   unsigned short *mode);
 
 /**
  * Generate the full pathname of a tree entry based from the root of the