docs: Stop describing Docker as experimental.

It's not an accurate descripton for an image that's been used in
production for many years, and we fully support.

docs/production/deployment.md

@@ -38,12 +38,22 @@ our next major release has a reliable install experience.
 
 ## Zulip in Docker
 
-Zulip has an officially supported, experimental
-[docker image](https://github.com/zulip/docker-zulip). Please note
-that Zulip's [normal installer](install.md) has been
-extremely reliable for years, whereas the Docker image is new and has
-rough edges, so we recommend the normal installer unless you have a
-specific reason to prefer Docker.
+In addition to the [standard installer](./install.md), Zulip has an
+[official Docker image](https://github.com/zulip/docker-zulip).
+
+How should you decide whether to use the Docker image? Our experience
+is that Docker moderately increases the effort required to install,
+maintain and upgrade a Zulip installation, especially for system
+administrators that are not used to operating production services
+using Docker.
+
+So we recommend using the Docker image if and only if your
+organization has a preference for deploying services using Docker.
+
+Zulip's [backup tool][backups] supports migrating between Docker and a
+standard installation, so you can change your mind later.
+
+[backups]: https://zulip.readthedocs.io/en/stable/production/export-and-import.html#backups
 
 ## Zulip installer details
 

docs/production/install.md

@@ -4,9 +4,9 @@ You can choose from several convenient options for hosting Zulip:
 
 - Follow these instructions to **install a self-hosted Zulip server on a system
   of your choice**.
+- Use Zulip's [Docker image](deployment.md#zulip-in-docker).
 - Use a preconfigured
   [DigitalOcean droplet](https://marketplace.digitalocean.com/apps/zulip?refcode=3ee45da8ee26)
-- Use Zulip's [experimental Docker image](deployment.md#zulip-in-docker).
 - Use [Zulip Cloud](https://zulip.com/plans/) hosting. Read our [guide to choosing between Zulip Cloud and
   self-hosting](https://zulip.com/help/zulip-cloud-or-self-hosting).