chore(windows): Remove "Switch Keyman Off" hotkey as it has the same action as the default language hotkey

**Describe the bug**

When Shift+Alt+O is pressed, Keyman is supposed to be turned off; however it is not obvious to the users how this works. Keyman keyboard seems to be running still as one can switch to a desired keyboard using language switcher or keyboard menu from the taskbar.

**To Reproduce**

1. Go to 'Configuration > Hotkeys'
2. Check and see the hotkey for 'Switch Keyman Off' is "Shift+Alt+O"
3. Press the key combo to switch Keyman off
4. Now, click on the ENG on the taskbar to change the keyboard to any other Keyman keyboard
5. See error

**Expected behavior**

From the users point of view, when Keyman is switched off, no Keyman keyboard should be working when chosen from the Windows language list in the Language Preferences.

---

**Keyman for Windows:**
- OS: Windows 10 Pro 1909 x64
- Keyman version: 14.0.221-beta
- Target Application: self