feat(angular): remove IonBackButtonDelegate (#29030)

Issue number: Internal

---------

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## What is the current behavior?
<!-- Please describe the current behavior that you are modifying. -->

We currently export two versions of the `ion-back-button` angular
implementation: `IonBackButton` and `IonBackButtonDelegate`.

## What is the new behavior?
<!-- Please describe the behavior or changes that are being added by
this PR. -->

- Removes `IonBackButtonDelegate` in favor of `IonBackButton`

## Does this introduce a breaking change?

- [x] Yes
- [ ] No

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  If this introduces a breaking change:
1. Describe the impact and migration path for existing applications
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  2. Update the BREAKING.md file with the breaking change.
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See
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- The `IonBackButtonDelegate` class has been removed in favor of
`IonBackButton`.

  ```diff
  - import { IonBackButtonDelegate } from '@ionic/angular';
  + import { IonBackButton } from '@ionic/angular';
  ```



## Other information

<!-- Any other information that is important to this PR such as
screenshots of how the component looks before and after the change. -->

Author: sean-perkins

BREAKING.md

@@ -29,6 +29,8 @@ This is a comprehensive list of the breaking changes introduced in the major ver
   - [Select](#version-8x-select)
   - [Textarea](#version-8x-textarea)
   - [Toggle](#version-8x-toggle)
+- [Framework Specific](#version-8x-framework-specific)
+  - [Angular](#version-8x-angular)
 
 <h2 id="version-8x-browser-platform-support">Browser and Platform Support</h2>
 
@@ -198,4 +200,15 @@ For more information on styling toast buttons, refer to the [Toast Theming docum
 
 <h4 id="version-8x-toggle">Toggle</h4>
 
-- The `legacy` property and support for the legacy syntax, which involved placing an `ion-toggle` inside of an `ion-item` with an `ion-label`, have been removed. For more information on migrating from the legacy toggle syntax, refer to the [Toggle documentation](https://ionicframework.com/docs/api/toggle#migrating-from-legacy-toggle-syntax).
+- The `legacy` property and support for the legacy syntax, which involved placing an `ion-toggle` inside of an `ion-item` with an `ion-label`, have been removed. For more information on migrating from the legacy toggle syntax, refer to the [Toggle documentation](https://ionicframework.com/docs/api/toggle#migrating-from-legacy-toggle-syntax).
+
+<h2 id="version-8x-framework-specific">Framework Specific</h2>
+
+<h4 id="version-8x-angular">Angular</h4>
+
+- The `IonBackButtonDelegate` class has been removed in favor of `IonBackButton`.
+
+  ```diff
+  - import { IonBackButtonDelegate } from '@ionic/angular';
+  + import { IonBackButton } from '@ionic/angular';
+  ```

packages/angular/src/index.ts

@@ -5,8 +5,6 @@ export { SelectValueAccessorDirective as SelectValueAccessor } from './directive
 export { TextValueAccessorDirective as TextValueAccessor } from './directives/control-value-accessors/text-value-accessor';
 export { IonTabs } from './directives/navigation/ion-tabs';
 export { IonBackButton } from './directives/navigation/ion-back-button';
-// TODO FW-5889
-export { IonBackButton as IonBackButtonDelegate } from './directives/navigation/ion-back-button';
 export { IonNav } from './directives/navigation/ion-nav';
 export { IonRouterOutlet } from './directives/navigation/ion-router-outlet';
 export {