chore(docs): update cloud docs (#37652)

Co-authored-by: Lennart <[email protected]>

Author: littlemarcus

docs/docs/how-to/cloud/adding-a-custom-domain.md

@@ -73,6 +73,8 @@ After the domain is validated, we'll generate a free SSL certificate via Let's E
 
 **Note**: DNS records need to be fully propagated in order to properly verify the certificates. If not, SSL certification generation will fail.
 
+SSL certificates generated by Gatsby will automatically update with no action required on your end. If you add a [custom SSL certificate](https://support.gatsbyjs.com/hc/en-us/articles/1500003044001-Adding-a-Custom-SSL-Certificate), you will need to generate and reupload a new certificate before the current certificate expires.
+
 ## 5. Finish
 
 Once your custom domain has the **"HTTPS On"** label next to it, you should be able to visit it to see your site live.  

docs/docs/reference/cloud/gatsby-cloud-environment-variables.md

@@ -10,7 +10,7 @@ The environment variables below allow you to configure features of Gatsby Cloud:
 - `NPM_REGISTRY`: Use to set the URL of a private registry.
 - `YARN_FLAGS`: Flags that are passed through to the yarn command.
 - `NODE_OPTIONS`: Passed through as options for Node.js. For example, - `NODE_OPTIONS=--max-old-space-size=4096`.
-- `PREFIX_PATHS`: Set to true to enable the `--prefix-paths` flag during `gatsby build`. See the docs on [prefix-paths](../../how-to/previews-deploys-hosting/path-prefix.md).
+- `PREFIX_PATHS`: Set to true to enable the `--prefix-paths` flag during `gatsby build`. See the docs on [prefix-paths](/docs/how-to/previews-deploys-hosting/path-prefix/).
 
 ## Read-only variables