test(spinner): add transform test back (#31017)

Issue number: N/A

---------

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## What is the current behavior?
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While working on the migration for the spinner to Ionic Modular, I
noticed that we had a [Transform test
page](https://github.com/ionic-team/ionic-framework/blob/2b5b9137fc164c2f3305e493510a884c0afbfcf0/core/src/components/spinner/test/transform/index.html#L5)
without any context of why it was there. I found out that it's meant for
a [bug](https://github.com/ionic-team/ionic-framework/issues/19247) that
was reported in v4 and we did have a
[test](https://github.com/ionic-team/ionic-framework/pull/24643/changes#diff-7b7ff84d3845fbde015775aa2da960310e80f79ec01b1f4a5957d751eddce7c9R1)
for it at some point but it was removed at a later date because it was
[discovered](https://github.com/ionic-team/ionic-framework/pull/25259)
that it wasn't doing anything.

So we don't have any coverage of it if there's a regression.

## What is the new behavior?
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this PR. -->

- Added a test to prevent a regression

## Does this introduce a breaking change?

- [ ] Yes
- [x] No

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## Other information

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screenshots of how the component looks before and after the change. -->

How to test:
1. Be on your local
2. Navigate to `spinner.scss`
3. Update the following code snippet:
```diff
- :host(.spinner-circular) svg {
+ :host(.spinner-circular) {
  animation: spinner-circular linear infinite;
}
```
4. By making this code change, we are introducing the [original
issue](https://github.com/ionic-team/ionic-framework/pull/24643/changes#diff-fa8f6fb72eceb39e2482c0dbc083f69ecdabd411be541c21947f8e8e9bf9ee48L118).
5. Run the test
6. Notice that it fails
7. Undo the code change
8. Run the test
9. Verify that it passes