chore(windows): remove references to SRegKey_InstalledKeyboards_CU

`SRegKey_InstalledKeyboards_CU` is no longer relevant, because keyboards are installed LM. However, there is legacy code that still references this key. Cleaning this up will probably produce additional chores, e.g. `KeyboardInstalled(KeyboardName, FInstByAdmin)` should drop the `FInstByAdmin` parameter, which will cascade a little.

```
6 results - 5 files

windows\src\engine\kmcomapi\processes\keyboard\kpuninstallkeyboard.pas:
89 RootKey := HKEY_CURRENT_USER;
90: Path := '\'+SRegKey_InstalledKeyboards_CU+'\'+KeyboardName;
91 end;

windows\src\engine\kmcomapi\processes\visualkeyboard\KPUninstallVisualKeyboard.pas:
70 RootKey := HKEY_CURRENT_USER;
71: Path := '\'+SRegKey_InstalledKeyboards_CU+'\'+KeyboardName;
72 end;

windows\src\engine\kmcomapi\util\utilkeyman.pas:
109 begin
110: Result := SRegKey_InstalledKeyboards_CU+'\'+GetShortKeyboardName(FileName);
111 end;

142
143: if OpenKeyReadOnly(SRegKey_InstalledKeyboards_CU+'\'+KeyboardName) and ValueExists(SRegValue_KeymanFile) then
144 begin

windows\src\global\delphi\general\RegistryKeys.pas:
211 SRegKey_InstalledKeyboards_LM = SRegKey_KeymanEngine_LM + '\Installed Keyboards'; // LM
212: SRegKey_InstalledKeyboards_CU = SRegKey_KeymanEngine_CU + '\Installed Keyboards'; // CU TODO:REMOVE THIS NOT USED
213

windows\src\global\delphi\visualkeyboard\VisualKeyboardInfo.pas:
81 RootKey := HKEY_CURRENT_USER;
82: Path := '\'+SRegKey_InstalledKeyboards_CU+'\';
83 end;
```