FLAG_UPDATE webhook shows incorrect states when removing segment override (and missing when versioning enabled)

[gagantrivedi]

Description

There's an inconsistency in the FLAG_UPDATE webhook behavior when removing a segment override from an environment, with different problems depending on whether versioning is enabled.

Current Behavior

Without versioning:

• FLAG_UPDATE webhook is triggered ✅
• Problem: Both new_state and previous_state contain the same data - the feature state that was removed

With versioning:

• FLAG_UPDATE webhook is not triggered at all ❌

Expected Behavior

1. FLAG_UPDATE should be triggered consistently for both versioning and non-versioning environments
2. The webhook payload should accurately reflect the state change:
   • previous_state: The segment override that is being removed
   • new_state: The environment default feature state (which will now apply after the override is removed)

Proposed Solution

• Ensure FLAG_UPDATE is triggered when removing segment overrides in versioned environments
• Populate new_state with the environment default feature state?
• Populate previous_state with the segment override being removed