Kibana version: 8.0.0

Browser version: chrome latest

Browser OS version: OS X

Original install method (e.g. download page, yum, from source, etc.): from source

Describe the bug: If user selects auto interval on date histogram for x-axis bucket - Kibana is displaying it as timestamp per 0 milliseconds when the bucket details are collapsed

Steps to reproduce:

1. Pull latest Kibana 8.0.0 from source and build/run it
2. Install sample data say flights
3. Click on visualize and create area chart -> pick auto for interval for date histogram bucket type on x axis
4. Collapse the x-axis bucket details - Kibana displays the interval as timestamp per 0 milliseconds

Screenshots (if relevant):