Update .gitreview default branch
Update .gitreview default branch

Change-Id: Iafe74989ca810dadd834910f9b193f00f58b339b

opennetworkinglab/spring-open,opennetworkinglab/spring-open,opennetworkinglab/spring-open,opennetworkinglab/spring-open,opennetworkinglab/spring-open,opennetworkinglab/spring-open