Change the background color for the smooth slider over plots (#3427)

Author: sroy3

webview/src/plots/components/styles.module.scss

@@ -48,7 +48,7 @@ $gap: 20px;
   position: absolute;
   bottom: 0;
   width: 100%;
-  background-color: $plot-block-bg-color;
+  background-color: $bg-color;
   color: $fg-color;
   padding: 10px;
   display: none;