fix(overlays): announce info after opening based on platform (#30025)

Issue number: internal

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## What is the current behavior?
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PR https://github.com/ionic-team/ionic-framework/pull/29951 would hide
the overlays from screen readers while animating. This allows the
element to navigate to its correct destination for screen readers to
interact with. Otherwise, the focus rings would never appear. However,
this ended up breaking the interaction for iOS.

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

- Overlays are hidden from screen readers while animating only if the
platform is `android`. Since the original issue only applied to Android
devices.

## 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. -->

Dev build: `8.4.1-dev.11732033492.170e160c`

Test on iOS and Android devices.