fix: ebay-line-chart tooltip and ebay-lightbox-modal have a z-index problem

[figueiredo-lucas]

Bug Report

eBayUI Version: 11.2.0

Description

I want to use the ebay-line-chart within a ebay-lightbox-modal, but the tooltip has a smaller z-index than the modal, which causes it not to show up.

Workaround

Manually increase the tooltip z-index:

.highcharts-tooltip-container {
    z-index: 99999999 !important;
}

Screenshots

Modal using a very high z-index

Tooltip z-index is very small

This would be the expected outcome: