bug(material/tabs): tab body height animation is broken

### Is this a regression?

- [ ] Yes, this behavior used to work in the previous version

### The previous version in which this bug was not present was

_No response_

### Description

You can even see this behaviour in the tab example in the docs https://material.angular.dev/components/tabs/examples
scroll down to the "Tab group that keeps its content inside the DOM when it's off-screen." example
it instantly hides the first tab content when u click the second, instead of waiting for the animation to complete, leading to a glitchy stutter

### Reproduction

look at angular material's own docs ^

### Expected Behavior

it should keep the content showing until the animation is completely done

### Actual Behavior

it glitches and hides instantly

### Environment

- Angular:
- CDK/Material:
- Browser(s):
- Operating System (e.g. Windows, macOS, Ubuntu):

Reproduce the problem in the Angular Material docs' "Tab group that keeps its content inside the DOM when it's off-screen" example. Start by tracing the tab body height animation and content visibility behavior when switching tabs. Done means the previous tab content remains visible until its animation finishes, without the reported stutter.

Written by the indexing model from the issue text.