feat(mac): remove obsolete configuration UI 🍎

[sgschantz]

Now that the Keyman Configuration app is available to install and manage keyboard packages, delete the old configuration interface accessed through the Keyman menu on the input method.

Build-bot: release:mac

User Testing

• TEST_INPUT_METHOD

1. Install the version of Keyman associated with this PR
2. Verify that the Configuration... menu is no longer available in the Keyman input method
3. Verify that the Configuration... button is no longer available in the About window
4. Confirm that the input method otherwise behaves as expected (aside from outstanding issues)

.

[keymanapp-test-bot]

User Test Results

Test specification and instructions

• ✅ TEST_INPUT_METHOD (PASSED) (notes)

Test Artifacts

• macOS
  • Keyman for macOS (.dmg)
  • Keyman for macOS (.pkg)

[mcdurdin]

This looks generally okay, except I think we should, if possible, continue to have a Configuration menu item in the IM menu

[Meng-Heng]

Test Specs

1. Keyman version 19.0.286-alpha 16570
2. macOS Sequoia

Test Results

• TEST_INPUT_METHOD (PASSED):

1. Restart machine as prompted
2. VERIFIED:
   • The Configuration... menu is no longer available in the Keyman input method
   • The Configuration... button is no longer available in the About window
3. VERIFIED:
   • Disable, Enable, Install, and Remove keyboards behaves as expected
   • Enable a keyboard to type in Notes work as expected
   • The About and On-screen keyboard show up as expected.