bug(iOS): selecting text and then backspacing also deletes the character before the selection

### Describe the bug

From https://community.software.sil.org/t/ios-and-android-undesirable-behaviour-with-selected-text/6986:

> Using Keyman 15.0.272 on iOS and Android (and also a KAB keyboard) I’ve had users report and I’ve reproduced some undesirable behaviours around selected words.
>
> On iOS (my iPhone 7 is 15.5):
> If I double tap to select a word not at the start of a line then type backspace or something else to replace it, then the space before that selected word is removed too. Other keyboards don’t remove the space. The extra removal of the space occurs in my NaijaType keyboard and EuroLatin keyboards in Keyman.

### Reproduce the bug

1. Type a full sentence of text.
2. Select a couple of words in the middle of the sentence (via double-tap) that is not at the start of a line.
3. Type backspace.

Worth investigation re: step 3: "or something else to replace it."

### Expected behavior

Backspacing the selected text should erase it, and _only_ it.

### Related issues

_No response_

### Keyman apps

- [ ] Keyman for Android
- [X] Keyman for iPhone and iPad
- [ ] Keyman for Linux
- [ ] Keyman for macOS
- [ ] Keyman for Windows
- [ ] Keyman Developer
- [ ] KeymanWeb
- [ ] Other - give details at bottom of form

### Keyman version

15.0.272

### Operating system

iOS 15.5

### Device

iPhone 7

### Target application

Keyman

### Browser

_No response_

### Keyboard name

NaijaType, SIL EuroLatin

### Keyboard version

_No response_

### Language name

_No response_

### Additional context

_No response_