simplify Dockerfile FROM clause

Change-Id: I4b3db457741d72634568faed1ec229067673ca76

outyet/Dockerfile

diff --git a/outyet/Dockerfile b/outyet/Dockerfile
index 1612c5c..3fa58ff 100644
--- a/outyet/Dockerfile
+++ b/outyet/Dockerfile
@@ -1,2 +1,2 @@
-FROM golang:1-onbuild
+FROM golang:onbuild
 EXPOSE 8080