[Heatmap] Scrollbars appear on container size change

[flash1293]

Describe the bug
If a heatmap is configured to fill it's container element completely, changing the container size (e.g. by resizing the browser window), will change the size of the visible chart, but scrollbars will appear and the user can scroll into whitespace of the original size.

To Reproduce
Steps to reproduce the behavior:

1. Go to https://codesandbox.io/s/polished-snowflake-vwjqx
2. Reduce the browser height
3. A scrollbar appears

Expected behaviour
No scrollbar

Screenshots

It seems like the echAnchorMainTooltip element is keeping the element size:

Version (please complete the following information):

• OS: macOS
• Browser: Chrome 91
• Elastic Charts: 30.2.0

Additional context
Can be seen in the Lens heatmap integration as well

Kibana Cross Issues

• [Lens] Get Heatmap out of experimental status kibana#102036

Checklist

Delete any items that are not applicable to this issue.

• every related Kibana issue is listed under Kibana Cross Issues list
• kibana cross issue tag is associated to the issue if any kibana cross issue is present

[nickofthyme]

@flash I cannot reproduce this in Chrome nor Firefox going back all the way to 23.1.0 when Heatmap was added. Could you confirm this and reopen if still an issue. Thanks!

Screen.Recording.2021-07-22.at.10.23.39.AM.mp4