docs(material/progress-bar): remove old MDC guide

Removes a guide that should've been deleted when we moved the MDC components to stable.

Author: crisbeto

src/material/progress-bar/README.md

@@ -1,65 +1 @@
-This version of `<mat-progress-bar>` is built on top of
-[MDC Web](https://github.com/material-components/material-components-web).
-
-## How to use
-Assuming your application is already up and running using Angular Material, you can add this
-component by following these steps:
-
-1. Install Angular Material & MDC WEB:
-
-   ```bash
-   npm i material-components-web @angular/material
-   ```
-
-2. In your `angular.json`, make sure `node_modules/` is listed as a Sass include path. This is
-   needed for the Sass compiler to be able to find the MDC Web Sass files.
-
-   ```json
-   ...
-   "styles": [
-     "src/styles.scss"
-   ],
-   "stylePreprocessorOptions": {
-     "includePaths": [
-       "node_modules/"
-     ]
-   },
-   ...
-   ```
-
-3. Import the `MatProgressBarModule` and add it to the module that declares your component:
-
-   ```ts
-   import {MatProgressBarModule} from '@angular/material/progress-bar';
-
-   @NgModule({
-     declarations: [MyComponent],
-     imports: [MatProgressBarModule],
-   })
-   export class MyModule {}
-   ```
-
-4. Add use `<mat-progress-bar>` in your component's template, just like you would the normal
-   `<mat-progress-bar>`:
-
-   ```html
-   <mat-progress-bar [value]="42"></mat-progress-bar>
-   ```
-
-5. Add the theme and typography mixins to your Sass:
-
-   ```scss
-   @use '@angular/material' as mat;
-
-   $my-primary: mat.define-palette(mat.$indigo-palette);
-   $my-accent: mat.define-palette(mat.$pink-palette, A200, A100, A400);
-   $my-theme: mat.define-light-theme((
-     color: (
-       primary: $my-primary,
-       accent: $my-accent
-     )
-   ));
-
-   @include mat.progress-bar-theme($my-theme);
-   @include mat.progress-bar-typography($my-theme);
-   ```
+Please see the official documentation at https://material.angular.io/components/component/progress-bar