travis: Don't install oracle-java8
travis: Don't install oracle-java8

It's installed by default now, and it seems installing the PPA package
makes it fail.

Signed-off-by: Alexandre Montplaisir <0b9d8e7da097b5bbfe36e48cca5acfe475f18227@efficios.com>

alexmonthy/libdelorean-java,alexmonthy/libdelorean-java