Avoid pointing users to Oracle Java if possible

[sneumann]

Hi Team ENA / webin-cli,
the docs suggest to install Oracle Java:

read_docs/submit/general-guide/webin-cli.md

Line 31 in 51c25b1

- [ **Download Java** ](https://www.oracle.com/uk/java/technologies/downloads/#java17)

due to the Oracle licensing policy (https://www.mobilize.net/blog/oracle-java-licensing)
this should be avoided at all costs, and instead point to installing OpenJDK.
This issue is related to enasequence/webin-cli#149
Yours,
Steffen