[Test] Fix console warning in field_editor.test.tsx

[ananzh]

Description

Currently, unit test field_editor.test.tsx shows a console warning:

React.createElement: type is invalid -- expected a string (for built-in components) or a class/function (for composite components) but got: undefined. 

This warning is because EuiCodeEditor is missing in the mock of elastic/eui, which causes undefined EuiCodeEditor in the test.

PR Resolved:

#673

Test results

unit test for field_editor.test.tsx

yarn test:jest src/plugins/index_pattern_management/public/components/field_editor/field_editor.test.tsx -u
yarn run v1.22.5
$ node scripts/jest src/plugins/index_pattern_management/public/components/field_editor/field_editor.test.tsx -u
 PASS  src/plugins/index_pattern_management/public/components/field_editor/field_editor.test.tsx
  FieldEditor
    ✓ should render create new scripted field correctly (15 ms)
    ✓ should render edit scripted field correctly (5 ms)
    ✓ should show deprecated lang warning (4 ms)
    ✓ should show conflict field warning (4 ms)
    ✓ should show multiple type field warning with a table containing indices (4 ms)

 › 5 snapshots updated.
Snapshot Summary
 › 5 snapshots updated from 1 test suite.

Test Suites: 1 passed, 1 total
Tests:       5 passed, 5 total
Snapshots:   5 updated, 5 total
Time:        3.688 s, estimated 4 s

Overall test result:

Check List

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has javadoc added
• Commits are signed per the DCO using --signoff

[opensearch-ci-bot]

✅   DCO Check Passed 027410f

[tmarkley]

LGTM!

[tmarkley]

@ananzh I just noticed that you updated snapshots but didn't include the new snapshots in the PR. I'll fix that.