chore(web): removes old reference-doc from alpha that has completed its purpose

[jahorton]

I just remembered that I never deleted a gesture-engine document that existed to provide a reference when finally replacing the OSK's old input-handling scheme with the gesture-engine. That's been completed for a while now, so there's no reason to keep the old document around any longer.

@keymanapp-test-bot skip

[keymanapp-test-bot[bot]]

User Test Results

Test specification and instructions

User tests are not required

Test Artifacts

• Android
  • Keyman for Android apk
  • FirstVoices for Android 16.0 apk
  • FirstVoices Keyboards for Android apk
  • KeyboardHarness apk
  • Keyman for Android 16.0 apk
  • KMSample1 apk
  • KMSample2 apk
• Developer
  • Keyman Developer
  • Compiler Regression Tests
  • kmcomp.zip
• iOS
  • Keyman for iOS (simulator image) - build failure
  • FirstVoices Keyboards for iOS (simulator image) - build failure
• Keyboards
  • Test Keyboards
• Web
  • KeymanWeb Test Home
• Windows
  • Keyman for Windows
  • FirstVoices Keyboards for Windows
  • Text Editor (32 bit)
  • Text Editor (64 bit)

[keyman-server]

Changes in this pull request will be available for download in Keyman version 17.0.317-beta