fix(angular): remove invalid z-index style (#27559)

Issue number: N/A

---------

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

The Angular implementation of `ion-tabs` uses SASS styles in the inline
usage for styles:

```ts
styles: [`
  :host {
    z-index: $z-index-page-container;
  }
`]
```

However Angular is expecting CSS mark-up by default. This results in an
invalid value being assigned to the `z-index`.

![image
(10)](https://github.com/ionic-team/ionic-framework/assets/13732623/3a917c7e-bbb3-4ce2-afb9-d6d4f0d3824f)


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

- Removes the invalid style from the tabs stylesheet
- Removes unnecessary leading whitespace from the template

## Does this introduce a breaking change?

- [ ] Yes
- [x] No

<!-- If this introduces a breaking change, please describe the impact
and migration path for existing applications below. -->


## Other information

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screenshots of how the component looks before and after the change. -->

angular/src/directives/navigation/ion-tabs.ts

@@ -8,7 +8,7 @@ import { StackEvent } from './stack-utils';
 
 @Component({
   selector: 'ion-tabs',
-  template: ` <ng-content select="[slot=top]"></ng-content>
+  template: `<ng-content select="[slot=top]"></ng-content>
     <div class="tabs-inner">
       <ion-router-outlet #outlet tabs="true" (stackEvents)="onPageSelected($event)"></ion-router-outlet>
     </div>
@@ -29,7 +29,6 @@ import { StackEvent } from './stack-utils';
         height: 100%;
 
         contain: layout size style;
-        z-index: $z-index-page-container;
       }
       .tabs-inner {
         position: relative;