SDK only sends the event once per flag

[marandaneto]

💡 Motivation and Context

https://github.com/PostHog/posthog-ios-recorder/pull/6#discussion_r1354591017

💚 How did you test it?

📝 Checklist

• I reviewed the submitted code.
• I added tests to verify the changes.
• I updated the docs if needed.
• No breaking change or entry added to the changelog.

[marandaneto]

@neilkakkar I am tagging you on feature flag PRs but feel free to just "this is ok and makes sense" rather than line by line.
Since SDKs do different things sometimes, its always good to have a quick look before either introducing a new behaviour or the wrong one =D

[neilkakkar]

one comment to fix, otherwise LGTM!