Move predicate_label examples to predicate_id in sssom_schema.yaml

[matentzn]

Fixes #369.

The examples for the predicate_id slot where in the wrong slot (predicate_label), here we move them to be correct.

I have also added a single example for the predicate_label slot.

• [X] docs/ have been added/updated if necessary
• [ ] make test has been run locally
• [ ] tests have been added/updated (if applicable)
• [ ] CHANGELOG.md has been updated.

If you are proposing a change to the SSSOM metadata model, you must

• [ ] provide a full, working and valid example in examples/
• [ ] provide a link to the related GitHub issue in the see_also field of the linkml model
• [ ] provide a link to a valid example in the see_also field of the linkml model