devel/dbus-java: pin to openjdk8

Newer jdk versions give:
[00:00:10] org/freedesktop/dbus/AbstractConnection.java:13: error: as of release 9, '_' is a keyword, and may not be used as an identifier
[00:00:10] import static org.freedesktop.dbus.Gettext._;

PR: 292654
Approved-by: 0mp@ (maintainer)