misc/dashboard: show correct dir name in README

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/7909043

misc/dashboard/README

@@ -4,8 +4,8 @@
 
 The files in this directory constitute the continuous builder:
 
-godashboard/: an AppEngine server
-builder/:     gobuilder, a Go continuous build client
+app/:     an AppEngine server
+builder/: gobuilder, a Go continuous build client
 
 If you wish to run a Go builder, please email golang-dev@googlegroups.com