jvm.options renamed to jvm-[8|11].options not reflected in docs

#2860 renamed `jvm.options` to `jvm-8.options` and added `jvm-11.options` for Java 11, but [the docs](https://docs.janusgraph.org/operations/server/#configure-jvmoptions) still talk about `jvm.options`.

So, we just need to update the docs to mention both files for versions 0.6.1 and higher.

Open the operations/server documentation at the linked “configure jvmoptions” section and find references to `jvm.options`. Update the text to mention `jvm-8.options` and `jvm-11.options` for versions 0.6.1 and higher. Done means the documentation no longer presents `jvm.options` as the current filename.

Written by the indexing model from the issue text.