Remove oraclejdk7 from travis configuration, because it is no longer available.

see: travis-ci/travis-ci#7964 (comment) for details

Author: PascalSchumacher

.travis.yml

@@ -18,7 +18,6 @@ sudo: false
 
 jdk:
   - openjdk7
-  - oraclejdk7
   - oraclejdk8
 
 script: