use JDK8 for javadoc stage

Vladimir Kotal · Vladimir Kotal · commit d4c87e00156f · 2019-06-13T00:01:08.000+02:00
diff --git a/.travis.yml b/.travis.yml
@@ -82,5 +82,8 @@ jobs:
     install: true
   - stage: javadoc
     name: Upload javadocs to Github pages
+    os: linux
+    dist: trusty
+    jdk: oraclejdk8
     script: dev/javadoc.sh
     install: true
