deps: move the haybarn engine extra to 1.5.5rc1

vgi-python resolves a DuckDB-compatible engine lazily for expression-filter
evaluation, the transactor, and the statistics fixtures, preferring haybarn.
That floor still admitted 1.5.3rc10 and was resolving 1.5.4rc1, while the vgi
extension is now built against haybarn 1.5.5-rc1 — so the engine evaluating
filters in-process was a different build from the one on the other side of the
wire. Filter-evaluation skew is exactly the kind of difference that surfaces
as an unreproducible result rather than an error, so match them.

The integration workflow already moved to haybarn-v1.5.5-rc1 in the preceding
commit; this is the same move for the Python side.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MS3MkkHgE8pA3Aty7BnZKE

Author: rustyconover

pyproject.toml

@@ -49,7 +49,7 @@ dependencies = [
 # evaluation, the transactor, and the statistics fixtures. It is resolved
 # lazily in vgi/_duckdb.py: haybarn is preferred, stock duckdb is the
 # fallback. Neither is a hard dependency — install one via these extras.
-haybarn = ["haybarn>=1.5.3rc10"]
+haybarn = ["haybarn>=1.5.5rc1"]
 duckdb = ["duckdb>=1.5.3"]
 http = ["vgi-rpc[http]"]
 # Alternative HTTP server: granian moves socket I/O and HTTP parsing into Rust,