docs: remove content from using-ts-effectively

This content is out of date (in the Mirage case) and duplicated (in
the case of the duplicate types info). Remove it!

Author: chriskrycho

docs/ts/using-ts-effectively.md

@@ -286,68 +286,3 @@ Some common stumbling blocks for people switching to ES6 classes from the tradit
 ## Type definitions outside `node_modules/@types`
 
 By default, the TypeScript compiler loads all type definitions found in `node_modules/@types`. If the type defs you need are not found there and are not supplied in the root of the package you're referencing, you can register a custom value in `paths` in the `tsconfig.json` file. See the [tsconfig.json docs](http://www.typescriptlang.org/docs/handbook/compiler-options.html#compiler-options) for details.
-
-## ember-cli-mirage
-
-Mirage adds files from a nonstandard location to your application tree, so you'll need to tell the TypeScript compiler about how that layout works.
-
-For an app, this should look roughly like:
-
-```javascript
-{
-  "compilerOptions": {
-    "paths": {
-      // ...
-      "my-app-name/mirage/*": "mirage/*",
-    }
-  },
-  "include": [
-    "app",
-    "tests",
-    "mirage"
-  ]
-}
-```
-
-And for an addon:
-
-```javascript
-{
-  "compilerOptions": {
-    "paths": {
-      // ...
-      "dummy/mirage/*": "tests/dummy/mirage/*",
-    }
-  },
-  "include": [
-    "addon",
-    "tests"
-  ]
-}
-```
-
-Note that if Mirage was present when you installed ember-cli-typescript (or if you run `ember g ember-cli-typescript`), this configuration should be automatically set up for you.
-
-## "TypeScript is complaining about multiple copies of the same types!"
-
-You may sometimes see TypeScript errors indicating that you have duplicate type definitions for Ember, Ember Data, etc. This is usually the result of an annoying quirk of the way both npm and yarn resolve your dependencies in their lockfiles.
-
-### Just tell me how to fix it
-
-There are two options here, neither of them _great_:
-
-* manually edit `yarn.lock` or `package-lock.json` and merge the conflicting
-* add a ["resolutions"](https://yarnpkg.com/lang/en/docs/selective-version-resolutions/) key to your `package.json` with the version you want to install of the types you're installing:
-
-```javascript
-{
-  "resolutions": {
-    "**/@types/ember": "2.8.15"
-  }
-}
-```
-
-### Why is this happening?
-
-If you're using another package which includes these types, and then you trigger an upgrade for your own copy of the type definitions, npm and yarn will both try to preserve the existing installation and simply add a new one for your updated version. In most cases, this is sane behavior, because it prevents transitive dependency breakage hell. However, in the _specific_ case of type definitions, it causes TypeScript to get confused.
-