Update instructions for specifying group for repo.

Change-Id: I847cd0962bc158dd707cbc2fa7746e26b15e9179

GettingStarted.md

diff --git a/GettingStarted.md b/GettingStarted.md
index 34ce9a3..8580472 100644
--- a/GettingStarted.md
+++ b/GettingStarted.md
@@ -27,7 +27,7 @@
 new directory where you'd like it to live, and do the following:
 
 ```
-repo init -u sso://aiyprojects/manifest
+repo init -u sso://aiyprojects/manifest -g default,imx
 repo sync -j$(nproc)
 ```