Move all CSS into SCSS files for consistency and ease of colour maintenance etc. Fixes #2927

web/pgadmin/misc/static/explain/css/explain.css

@@ -53,13 +53,6 @@ td.explain-tooltip-val {
 
 }
 
-.pgadmin-explain-tooltip {
-  position: absolute;
-  opacity:0;
-  color: cornsilk;
-  background-color: #010125;
-}
-
 .pgadmin-tooltip-table {
   border-collapse: collapse;
   border-spacing: 1px;

web/pgadmin/misc/static/explain/scss/_explain.scss

@@ -0,0 +1,6 @@
+.pgadmin-explain-tooltip {
+  position: absolute;
+  opacity:0;
+  color: $color-gray-lighter;
+  background-color:  $color-gray-dark;
+}