Added a missing dispose of an AnimationController that was leaking a ticker.

[darrenaustin]

Description

We weren't disposing of an AnimationController in the material DataPicker implementation. This could lead to leaking a ticker when the picker was dismissed. This should take care of the exception mentioned in #32628.

Related Issues

Addresses the stack trace in #32628.

Tests

No changes to the tests.

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Breaking Change

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