scanner: Remove return doxygen annotation

Replace \returns with just Returns, as this is not a doxygen comment block.
(Avoids differing with the existing convention of \return for return values.)

Signed-off-by: Yong Bakos <ybakos@humanoriented.com>
Reviewed-by: Bryce Harrington <bryce@osg.samsung.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
diff --git a/src/scanner.c b/src/scanner.c
index c927275..3f181cd 100644
--- a/src/scanner.c
+++ b/src/scanner.c
@@ -586,7 +586,7 @@
  *
  * Upon error, this routine does not modify or set errno.
  *
- * \returns -1 on error, or a non-negative integer on success
+ * Returns -1 on error, or a non-negative integer on success
  */
 static int
 strtouint(const char *str)