Update outdated java version reference
It is only a comment, but can confuse those reading the code
Used 6.0 as an arbitrary elasticsearch.version value since it is version that required Java 8
#
# classname=foo.bar.BazPlugin
# description=My cool plugin
-# version=2.0
-# elasticsearch.version=2.0
-# java.version=1.7
+# version=6.0
+# elasticsearch.version=6.0
+# java.version=1.8
#
### mandatory elements for all plugins:
#
