fix: Error tooltip should have white text on red background. Not red text on red background

packages/grafana-ui/src/components/Tooltip/_Tooltip.scss

@@ -31,7 +31,7 @@ $popper-margin-from-ref: 5px;
 
   // Themes
   &.popper__background--error {
-    @include popper-theme($tooltipBackgroundError, $tooltipBackgroundError);
+    @include popper-theme($tooltipBackgroundError, $white);
   }
 
   &.popper__background--info {