docs-bug(mat-tree): Icons are broken on the Tree example page

[szoboszlaypali]

Documentation Feedback

The Tree examples page renders "chevron_right" instead of the icon itself for the new examples on the v21 page.

The new examples use <span class="material-symbols-outlined">chevron_right</span> instead of <mat-icon>chevron_right</mat-icon> and seemingly the docs site doesn't import Material Symbols Outlined

Affected documentation page

https://material.angular.dev/components/tree/examples