[NUI] Remove the legacy AccessibilityActivate code (#6223)
- `CSharp_Dali_ViewImpl_AccessibilityActivate` was removed in 2018 lol
However, at that time, NUI codes couldn't be removed together (Not sure)
- The reason `ViewImpl_AccessibilityActivate` was removed is
`Remove functions which using internal apis
Some binding functions use internal apis.
It caused error when dlopen csharp binder.`
- User can use Activated event with `View.AccessibilityActivated`
Signed-off-by: Seoyeon Kim <seoyeon2.kim@samsung.com>