Update docker compose guide to new syntax (#583)

Changed docker compose syntax to the new style (docker-compose is
deprecated and docker compose should now be used instead)

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Author: kilyinov

docs/admin/deploy/docker-compose/index.mdx

@@ -162,9 +162,9 @@ On the production server, run the following command inside the [./docker-compose
   # Go to the docker-compose configuration directory
   cd docker-compose
   # Start Sourcegraph with Docker Compose
-  docker-compose up
+  docker compose up
   # OR you can start Sourcegraph with Docker Compose in a detached mode
-  docker-compose up -d
+  docker compose up -d
 ```
 
 To check if the server is ready, the `sourcegraph-frontend-0` service must be displayed as healthy: