fix: invalid schema field for plugin fault-injection

[nic-chen]

What this PR does / why we need it:

refer to:
https://json-schema.org/understanding-json-schema/reference/array.html
In JSON Schema, it should use items to define the array item type, not item

Pre-submission checklist:

• Did you explain what problem does this PR solve? Or what new features have been added?
• Have you added corresponding test cases?
• Have you modified the corresponding document?
• Is this PR backward compatible? If it is not backward compatible, please discuss on the mailing list first

[Firstsawyou]

LGTM.