Fix formatting of Mongoose compatibility table

Author: alexbevi

docs/compatibility.md

@@ -18,7 +18,7 @@ Below are the [semver](http://semver.org/) ranges representing which versions of
 
 | MongoDB Server |                    Mongoose                    |
 | :------------: | :--------------------------------------------: |
-|     `8.x`      |                 `^8.7.0 | ^9.0.0`              |
+|     `8.x`      |                 `^8.7.0 \| ^9.0.0`             |
 |     `7.x`      |            `^7.4.0 \| ^8.0.0 \| ^9.0.0`        |
 |     `6.x`      |            `^7.0.0 \| ^8.0.0 \| ^9.0.0`        |
 |     `5.x`      |            `^6.0.0 \| ^7.0.0 \| ^8.0.0`        |