Use openjdk8 instead of oraclejdk8

SIkebe · SIkebe · commit 8ca65b8c756c · 2019-08-08T01:41:16.000+09:00
diff --git a/.travis.yml b/.travis.yml
@@ -2,7 +2,7 @@ language: scala
 scala:
   - 2.13.0
 jdk:
-  - oraclejdk8
+  - openjdk8
 env:
   - TRAVIS_NODE_VERSION="4"
 install:
