Update `ajv` from 8.11.0 to 8.12.0

[legobeat]

Updates pinned dependency ajv to latest.

Release Notes 8.12.0:

• fix JTD serialisation (remove leading comma in objects with only optional properties) (https://github.com/ajv-validator/ajv/pull/2190, @piliugin-anton)
• empty JTD "values" schema (https://github.com/ajv-validator/ajv/pull/2191)
• empty object to work with JTD utility type (https://github.com/ajv-validator/ajv/pull/2158, @erikbrinkman)
• fix JTD "discriminator" schema for objects with more than 8 properties (https://github.com/ajv-validator/ajv/pull/2194)
• correctly narrow "number" type to "integer" (https://github.com/ajv-validator/ajv/pull/2192, @JacobLey)

Release Notes 8.11.2:

Update dependencies Export ValidationError and MissingRefError (https://github.com/ajv-validator/ajv/pull/1840, @dannyb648)

8.11.1 was pre-release of 8.11.2

Diffs

Source diff `v8.12.0...v8.11.0

Package diff `ajv@8.12.0...ajv@8.11.0

[legobeat]

Closing in favor of #796 (changed branch name to conform with contributing guidelines)