Switched coveo analytics mode from default EP to legacy

[lamATnginx]

Proposed changes

Closes https://github.com/nginxinc/docs-platform/issues/387

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING document
• If applicable, I have added tests that prove my fix is effective or that my feature works
• If applicable, I have checked that any relevant tests pass after adding my changes
• I have updated any relevant documentation (README.md and CHANGELOG.md)

[lamATnginx]

Deployed to dev. Check-out the Network tab in https://docs-dev.nginx.com/search.html#q=proxy versus https://docs.nginx.com/search.html#q=proxy to see search events are being properly registered for Coveo. Example:

On an operation to just click a link:

Before:

After: