Fix nit in README.md.

Change-Id: I5fe58ca85f39f1f92f2da17e7d220209c23331cb

README.md

diff --git a/README.md b/README.md
index b36c4f9..19fc1a6 100644
--- a/README.md
+++ b/README.md
@@ -10,7 +10,7 @@
 
     go install github.com/google/gitfs/cmd/gitfs-multifs
     mkdir /tmp/mnt
-    gitfs-multifs -cache /tmp/cache -gitiles https://android.googlesource.com/  /tmp/mnt &
+    gitfs-multifs -gitiles https://android.googlesource.com/  /tmp/mnt &
 
 To create a workspace "ws" corresponding to the latest manifest version