Geomaps's scale is hardly visible when using `ArcGIS MapServer` as layer type

**Steps to reproduce**: * Create a new panel and select `Geomap` as type * Set `Map Layers > Layer Type` to `ArcGIS MapServer` * Enable `Map Controls > Show scale` **Actual Result**: The scaling bar at the bottom left is in a light gray and thus hardly visible because the map has a light colorscheme. **Expected Result** I'd like to be able to actually see the scaling bar. **Relevant WCAG Criteria:** [#.#.# WCAG Criterion](link to https://www.w3.org/WAI/WCAG21/quickref/?versions=2.0) n/a **Environment**: - Grafana version: 9.1.6 - Data source type & version: Prometheus (though it isn't dependant on the datasource to reproduce) - User OS & Browser: NixOS 22.05, Firefox 105.0 (64-bit)