bug: pull to refresh ios - content transforms which leaves blank space when scrolling

# Bug Report

**Ionic version:**
[x] **4.x**

**Current behavior:**
Pull to refresh. When performing this in chrome/safari/android content receives `overflow: hidden`.
But on iOS device it's possible to scroll content during refresh action. And then it looks very strange: Spinner disappears and just background left over the screen.

**Expected behavior:**
I think in every device content should get `overflow: hidden`

**Related code:**

Looks like the problem in next method in line 656:

https://github.com/ionic-team/ionic/blob/3937101e5c2b181a6b7926eb8386c22b0f887716/core/src/components/refresher/refresher.tsx#L655-L669

But I don't understand what does it mean here, this nativeRefresher and why in this case `overflow: hidden` shouldn't be set on ion-content

Start in core/src/components/refresher/refresher.tsx around lines 655-669 and inspect how nativeRefresher affects the overflow behavior. Reproduce pull-to-refresh scrolling on an iOS device, then compare it with Chrome, Safari, and Android. Done means the refresh spinner remains visible without blank space while content cannot scroll during the refresh action.

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