docs: remove references to animations package

[wbreakell]

Angular Material no longer depends on the @angular/animations package and it's no longer installed in the ng add schematic (#30446).

[wbreakell]

Hi @adolgachev and @andrewseguin, just a gentle nudge to ask for your review on this PR.

[crisbeto]

This PR was merged into the repository. The changes were merged into the following branches:

• main: 3a43de9
• 21.0.x: d86969f

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