Restore [] where default arguments are not keywords

Reverts some changes of d13fdd97cc8e.
diff --git a/Doc/library/curses.rst b/Doc/library/curses.rst
index 0b8b7c9..f31b9c5 100644
--- a/Doc/library/curses.rst
+++ b/Doc/library/curses.rst
@@ -1091,7 +1091,7 @@
    rendition (as set by :meth:`bkgdset`) merged into them.
 
 
-.. method:: window.scroll(lines=1)
+.. method:: window.scroll([lines=1])
 
    Scroll the screen or scrolling region upward by *lines* lines.