Many hosting environments allow you to update plugins using the Craft Control Panel directly within your staging or production environments.
However, this is generally considered bad practice as it makes it very difficult to keep your local, staging and production environments in sync.
As well as being bad practice, updating plugins within staging and production is incompatible with load balanced environments like Servd. Your update request will only run on one of potentially many running instances of your application, leaving each of them in an incompatible state.
For these reasons Servd requires users to follow a uni-direction development flow, starting with local development where installing plugins is fine.
Update a Plugin Locally
Get your project up and running in a local development environment. This might be ddev, Docker or MAMP. Any of these are fine as long as your Craft project is running on your local machine.
Using the Craft Control Panel's Plugin Store, or `composer` on the command line, update the plugin you need. If you are using Project Config to sync changes between environments, make sure you've also updated the plugin in Craft's settings.
Using `git` on the command line, or a visual git client, check to make sure your composer.json and composer.lock files (and optionally your project config files) have been updated and are ready to be committed.
Create a new commit and push your git repo.
Build a new bundle in Servd from your new commit and deploy it to one of your environments.
Your plugin is now updated!