add deprecation notice

Author: LiamConnors

_posts/plotly_js/maps/density-mapbox/2019-08-16-basic_density_mapbox_example.html

@@ -3,16 +3,15 @@
 language: plotly_js
 layout: base
 suite: tile-density-heatmaps
-order: 5
+order: 7
 sitemap: false
 arrangement: horizontal
 markdown_content: |
-<strong>> Mapbox traces are deprecated and may be removed in a future version of Plotly.js.</strong>
+  **Mapbox traces are deprecated and may be removed in a future version of Plotly.js.**
 
   Earlier examples use traces that render with [Maplibre GL JS](https://maplibre.org/maplibre-gl-js/docs/).
   These traces were introduced in Plotly.js 2.35.0 and replace Mapbox-based tile maps,
   which are now deprecated. Here's one of the earlier examples written using the Mapbox-based `densitymapbox` trace.
-
 ---
 var data = [
   {type: "densitymapbox", lon: [10, 20, 30], lat: [15, 25, 35], z: [1, 3, 2],