bug(mac): backspace is removing two characters in text input for github.com

### Describe the bug

I can't find anywhere else that produce this issue, except on github.com's text inputs, but the video below shows a much more unexpected behavior.

https://github.com/user-attachments/assets/52d738b9-c113-421a-b4f9-9896c5b8fd70

### Reproduce the bug

1. Install Keyman Configuration for macOS from https://github.com/keymanapp/keyman/pull/16339
2. After doing the final test (TEST_REPAIR_INSTALL) that I got to type with the keyboard
3. Install and switch to US Basic keyboard in Keyman
4. Start typing in GitHub's comment text input; e.g. Text input
5. Hit backspace one time
6. Two character removes
7. Type github's text input
8. Hit backspace one time
9. The spaces are removed as shown in the video.

### Expected behavior

Backspace one remove only one character at the cursor pointer.

### 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

Keyman-19.0.267-alpha-test-16339

### Operating system

macOS Sequoia

### Device

MacBook Pro 2019

### Target application

github.com

### Browser

Brave

### Keyboard name

basic_kbdus

### Keyboard version

_No response_

### Language name

_No response_

### Additional context

_No response_