[8.x] [chore] Delete deprecated avatars (#205448) (#206532)

# Backport

This will backport the following commits from `main` to `8.x`:
- [[chore] Delete deprecated avatars
(#205448)](#205448)

<!--- Backport version: 8.9.8 -->

### Questions ?
Please refer to the [Backport tool
documentation](https://github.com/sqren/backport)

<!--BACKPORT [{"author":{"name":"Clint Andrew
Hall","email":"[email protected]"},"sourceCommit":{"committedDate":"2025-01-07T22:21:21Z","message":"[chore]
Delete deprecated avatars (#205448)\n\n## Summary\r\n\r\nAs titled.
Delete deprecated avatars, replace stray usage.\r\n\r\n<img
width=\"1021\" alt=\"Screenshot 2025-01-02 at 4 38
33 PM\"\r\nsrc=\"https://github.com/user-attachments/assets/01e8045c-5209-4926-a5da-f04aa65ac76e\"\r\n/>","sha":"292111b0d694254cabc23df5751d2a9007794e91","branchLabelMapping":{"^v9.0.0$":"main","^v8.18.0$":"8.x","^v(\\d+).(\\d+).\\d+$":"$1.$2"}},"sourcePullRequest":{"labels":["review","release_note:skip","backport
missing","v9.0.0","backport:prev-minor","ci:build-storybooks","Team:Obs
AI
Assistant"],"number":205448,"url":"https://github.com/elastic/kibana/pull/205448","mergeCommit":{"message":"[chore]
Delete deprecated avatars (#205448)\n\n## Summary\r\n\r\nAs titled.
Delete deprecated avatars, replace stray usage.\r\n\r\n<img
width=\"1021\" alt=\"Screenshot 2025-01-02 at 4 38
33 PM\"\r\nsrc=\"https://github.com/user-attachments/assets/01e8045c-5209-4926-a5da-f04aa65ac76e\"\r\n/>","sha":"292111b0d694254cabc23df5751d2a9007794e91"}},"sourceBranch":"main","suggestedTargetBranches":[],"targetPullRequestStates":[{"branch":"main","label":"v9.0.0","labelRegex":"^v9.0.0$","isSourceBranch":true,"state":"MERGED","url":"https://github.com/elastic/kibana/pull/205448","number":205448,"mergeCommit":{"message":"[chore]
Delete deprecated avatars (#205448)\n\n## Summary\r\n\r\nAs titled.
Delete deprecated avatars, replace stray usage.\r\n\r\n<img
width=\"1021\" alt=\"Screenshot 2025-01-02 at 4 38
33 PM\"\r\nsrc=\"https://github.com/user-attachments/assets/01e8045c-5209-4926-a5da-f04aa65ac76e\"\r\n/>","sha":"292111b0d694254cabc23df5751d2a9007794e91"}}]}]
BACKPORT-->

x-pack/platform/plugins/shared/observability_solution/observability_ai_assistant/public/index.ts

@@ -32,7 +32,6 @@ export type {
 };
 
 export { aiAssistantCapabilities } from '../common/capabilities';
-export { AssistantAvatar } from './components/assistant_avatar';
 export { ConnectorSelectorBase } from './components/connector_selector/connector_selector_base';
 export { useAbortableAsync, type AbortableAsyncState } from './hooks/use_abortable_async';
 export { useGenAIConnectorsWithoutContext } from './hooks/use_genai_connectors';

x-pack/solutions/observability/plugins/observability_ai_assistant_app/public/components/rca/rca_callout/index.tsx

@@ -19,8 +19,8 @@ import {
 } from '@elastic/eui';
 import React from 'react';
 import { i18n } from '@kbn/i18n';
-import { AssistantAvatar } from '@kbn/observability-ai-assistant-plugin/public';
 import { css } from '@emotion/css';
+import { AssistantIcon } from '@kbn/ai-assistant-icon';
 
 export function RootCauseAnalysisCallout({
   onClick,
@@ -46,7 +46,7 @@ export function RootCauseAnalysisCallout({
             `}
           >
             <EuiFlexGroup direction="row" alignItems="center" justifyContent="center">
-              <AssistantAvatar />
+              <AssistantIcon size="l" />
               <EuiFlexItem grow={false}>
                 <EuiTitle size="xs">
                   <h2>