terminal: don't exclude appengine

terminal_notwindows.go

diff --git a/terminal_notwindows.go b/terminal_notwindows.go
index 80edd32..b8bebc1 100644
--- a/terminal_notwindows.go
+++ b/terminal_notwindows.go
@@ -3,7 +3,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build linux,!appengine darwin freebsd openbsd
+// +build linux darwin freebsd openbsd
 
 package logrus