fix(avatar): remove avatar border on ionic theme (#30045)

Issue number: internal

---------

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## What is the current behavior?

- Removed avatar border with ionic theme, to align with UX/UI design.
- Updated snapshots

## Does this introduce a breaking change?

- [ ] Yes
- [x] No

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## Other information

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

[Avatar Ionic
Sample](https://ionic-framework-nimqjtxw7-ionic1.vercel.app/src/components/avatar/test/shape?ionic:theme=ionic)

core/src/components/avatar/avatar.ionic.scss

@@ -23,8 +23,6 @@
 
 :host(:not(.avatar-image)) {
   @include padding(var(--padding-top), var(--padding-end), var(--padding-bottom), var(--padding-start));
-
-  border: globals.$ion-border-size-025 globals.$ion-border-style-solid globals.$ion-primitives-neutral-800;
 }
 
 // Avatar Sizes