Update to JCodings 1.0.64 which supports Unicode 17

[eregon]

Summary

Update to JCodings 1.0.64 which supports Unicode 17, the latest release of Unicode.
The previous version, 1.0.63 supported Unicode 15.1 and is over a year old (https://github.com/jruby/jcodings/tags).
This brings consistency with the rest of TruffleString and TRegex already supporting Unicode 17.

Related Issues

• Link the relevant issue, design discussion, or other prior context if applicable.

Testing

• Describe the testing performed.

The mighty Graal gate and existing TruffleString tests.

Documentation

• no documentation updates are needed (AFAIK)

Contributor Checklist

• I have read the contribution guide.
• I have the right to contribute the submitted material under the project terms.
• I have updated tests and documentation where appropriate.
• If I used a coding assistant, I remain responsible for the entire contribution and have reviewed it accordingly.

[eregon]

I forgot to update the sha256, fixed now.
(unfortunately the CI doesn't run on push to a fork's branch)