Manually update buildah to v1.13.1

Should help with #791.

Signed-off-by: Miloslav Trmač <mitr@redhat.com>

vendor/github.com/mattn/go-isatty/isatty_others.go

@@ -1,10 +0,0 @@
-// +build !windows
-// +build !appengine
-
-package isatty
-
-// IsCygwinTerminal return true if the file descriptor is a cygwin or msys2
-// terminal. This is also always false on this environment.
-func IsCygwinTerminal(fd uintptr) bool {
-	return false
-}