Update Turing.jl to v0.39 for BayesianInference benchmarks

Updates Turing.jl from v0.38 to v0.39 in the BayesianInference benchmarks.
This update is compatible with the existing code as it only uses basic
Turing features (@model, NUTS) that are still supported.

Key changes in Turing v0.39:
- Updated VI interface to match AdvancedVI v0.4
- Removed Turing.Essential module (not used in benchmarks)
- @addlogprob! macro now exported from Turing (not used in benchmarks)

Tested locally with a simple model to verify functionality.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: ChrisRackauckas