refactor(cloudapp)!: remove deprecated `cloudapp` plugin

BREAKING CHANGE: the `cloudapp` plugin has been removed due to removed API.

plugins/cloudapp/README.md

-# CloudApp plugin
-
-## The CloudApp API is deprecated, so the plugin will be removed shortly
-
-[CloudApp](https://www.getcloudapp.com) brings screen recording, screenshots, and GIF creation to the cloud, in an easy-to-use enterprise-level app. The CloudApp plugin allows you to upload a file to your CloadApp account from the command line.
-
-To use it, add `cloudapp` to the plugins array of your `~/.zshrc` file:
-
-```zsh
-plugins=(... cloudapp)
-```
-
-## Requirements
-
-1. [Aaron Russell's `cloudapp_api` gem](https://github.com/aaronrussell/cloudapp_api#installation)
-
-2. That you set your CloudApp credentials in `~/.cloudapp` as a simple text file like below:
-   ```
-   email
-   password
-   ```
-
-## Usage
-
-- `cloudapp <filename>`: uploads `<filename>` to your CloudApp account, and if you're using
-  macOS, copies the URL to your clipboard.

plugins/cloudapp/cloudapp.plugin.zsh

-print -Pn "%F{yellow}"
-print "[oh-my-zsh] The CloudApp API no longer works, so the cloudapp plugin will"
-print "[oh-my-zsh] be removed shortly. Please remove it from your plugins list."
-print -Pn "%f"