Changing oraclejdk8 to openjdk8 in hopes that it will fix our Travis builds.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=263837785
diff --git a/.travis.yml b/.travis.yml
index 2203d86..b0be6fa 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -10,7 +10,7 @@
 
 jdk:
   - openjdk9
-  - oraclejdk8
+  - openjdk8
 
 env:
   global: