Update posthog-rs dependency to use latest crates.io release instead of git rev

[amitksingh1490]

Currently, our dependency on posthog-rs points to a specific git revision. We should update our dependency to use the latest published release on crates.io.

Reason:

• Improves dependency reliability and reproducibility
• Enables SemVer version locking
• Aligns with Rust ecosystem best practices

Steps:

1. Update Cargo.toml to use posthog-rs = "<latest-version>"
2. Remove the [patch] or git dependency section referencing the git rev
3. Run cargo update and fix any arising compatibility issues
4. Verify all tests pass with the new version

---

This improves project maintainability and streamlines future dependency upgrades.