Minor text agreement correction

Signed-off-by: daftgopher <daftgopher@users.noreply.github.com>

docs/plugins/structure-of-a-plugin.md

@@ -99,14 +99,14 @@ You may tweak these components, rename them and/or replace them completely.
 
 ## Connecting the plugin to the Backstage app
 
-There are three things needed for a Backstage app to start making use of a
+There are two things needed for a Backstage app to start making use of a
 plugin.
 
 1. Add plugin as dependency in `app/package.json`
 2. Import and use one or more plugin extensions, for example in
    `app/src/App.tsx`.
 
-Luckily these three steps happen automatically when you create a plugin with the
+Luckily both of these steps happen automatically when you create a plugin with the
 Backstage CLI.
 
 ## Talking to the outside world