Update JDK version in README.md

[ada-phillips]

Update developer setup instructions to refer to JDK 17

Closes #10650

Changes proposed in this pull request

• Update developer setup instructions for JDK 17

Testing

• Yes I tested this before submitting it.
• I also did a multiplayer test.

Review please

[Nightenom]

1.21 requires jdk 21, so might be worth going with that instead

[ada-phillips]

1.21 requires jdk 21, so might be worth going with that instead

Yeaaah, I thought about that, but I wasn't sure where that branch is in terms of priority/releasability? There seems to be a pretty sizable gulf between the release/main and release/1.21

Maybe I can do a PR to that branch for a README update for jdk 21?

[someaddons]

I think we should mention both, telling ppl that version/main uses jdk 17 and version/1.21 jdk 21

[Raycoms]

Please make a PR to 1.21 with the 21 java instructions then too, yes =)