Remove KUI CSS hacks/overrides in `opensearch_dashboards_react` and `data`

[joshuarrrr]

There are a couple comments in SASS files that indicate hacks to override styles from KUI. These need to be investigated and removed if no longer necessary.

https://github.com/search?q=repo%3Aopensearch-project%2FOpenSearch-Dashboards+kui+NOT+trackUI+path%3A%2F%5Esrc%5C%2Fplugins%5C%2Fopensearch_dashboards_react%2F+OR+path%3A%2F%5Esrc%5C%2Fplugins%5C%2Fdata%2F&type=code