VOL-1643 Update open-onu-adapter to use voltha-protos v3.0.0

It doesn't require any code changes other than updating the requirements file.

Change-Id: Ibd9bc380abfbd4e2104c22f31de7ace715446483
diff --git a/python/requirements.txt b/python/requirements.txt
index a7a5fce..ed7cbd7 100644
--- a/python/requirements.txt
+++ b/python/requirements.txt
@@ -1,2 +1,2 @@
-voltha-protos==2.1.2
-pyvoltha==2.3.7
+voltha-protos==3.0.0
+pyvoltha==2.3.8