bug(mac): excess backspace when deleting composed character in Google Docs

### Describe the bug

When typing in Google Docs with the Kenya (BTL) keyboard, backspacing over a composed characters causes the unaccented character to replace the accented/composed character AND the previous character.

### Reproduce the bug

Type:b^u
Output: bû
Type: backspace
Output: u

### Expected behavior

Type:b^u
Output: bû
Type: backspace
Output: bu

### Related issues

_No response_

### Keyman apps

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

### Keyman version

17

### Operating system

_No response_

### Device

_No response_

### Target application

Google Docs running in Google Chrome

### Browser

_No response_

### Keyboard name

Kenya (BTL)

### Keyboard version

_No response_

### Language name

_No response_

### Additional context

_No response_