Fix deprecated indexing of open call in windows displaysize

missed from #12807, only happens when running in mintty

Author: tkelman

base/stream.jl

@@ -362,7 +362,7 @@ function displaysize(io::TTY)
         if ispty(io)
             # io is actually a libuv pipe but a cygwin/msys2 pty
             try
-                h, w = map(x -> parse(Int, x), split(readstring(open(Base.Cmd(String["stty", "size"]), "r", io)[1])))
+                h, w = parse.(Int, split(readstring(open(Base.Cmd(String["stty", "size"]), "r", io).out)))
                 h > 0 || (h = default_size[1])
                 w > 0 || (w = default_size[2])
                 return h, w