chg: [mitre] bump to latest v18.1

[fukusuket]

Hello, and thank you for maintaining misp-galaxy :)

Since MITRE ATT&CK v18.1 was released on October 28, I updated Galaxy using gen-mitre.py. (If there is a more appropriate method to perform this update, I'll close this PR)

I have confirmed that the following two tests pass:

• ./jq_all_the_things.sh
• ./validate.sh

Additionally, this PR includes a couple of minor fixes:

• Added validation for the x_mitre_data_source_ref key in gen-mitre.py
• Updated the find command in validate.sh so that it works on both GNU and BSD systems

Thank you for your time.

[fukusuket]

One thing I am slightly concerned about in this PR is that, compared to the previous version, the elements under the "mitre_data_sources" key have been removed...,

• https://github.com/MISP/misp-galaxy/pull/1114/files#diff-75f117e4c2542271889ef61b186c9813481a6108eb2b37acc1ec35df4ab5f099L90

and I couldn’t determine the reason for this. I would appreciate it if you could review this point as well🙏

[adulau]

Thanks a lot for the PR.

The format changed significantly and we indeed need to review more deeply the impact of the change.

[fukusuket]

@adulau Thank you for providing your comments so quickly :)
I will also try to investigate the cause of the differences as much as I can on my side.