fix: browser integration tests do not cover `ajv2020` and `ajvjtd` umd bundles

## Description

The browser test runner only loads `bundle/ajv7.min.js` and `bundle/ajv2019.min.js`, while the build config also produces `ajv2020` and `ajvJTD` bundles. This leaves two published browser artifacts unverified in CI, so bundling/runtime regressions in those entrypoints can ship undetected.

**Severity**: `high`
**File**: `karma.conf.js`

## Expected Behavior

The code should handle this case properly to avoid unexpected errors or degraded quality.