style: ruff 0.17 formats Python blocks inside Markdown — reformat README_UNITY

The lock bump moved ruff 0.15.4 -> 0.17.1, whose `ruff format` now also
covers fenced Python in Markdown under src/; CI's `ruff format --check
src/ tests/` failed on four whitespace nits in this README.

Refs #1365

src/aco/lake/README_UNITY.md

@@ -235,7 +235,7 @@ df = ctx.load("core.encounter")
 
 # Columns are automatically renamed from Unity Catalog names
 assert "encounter_id" in df.columns  # Mapped from encntr_id
-assert "person_id" in df.columns     # Mapped from mbr_id
+assert "person_id" in df.columns  # Mapped from mbr_id
 ```
 
 ## Workspace Configuration
@@ -310,6 +310,7 @@ encounters = ctx.load("core.encounter")
 
 # Use in pipeline
 from aco.pipe import readmissions
+
 results = readmissions.pipeline.run(ctx.load)
 ```
 
@@ -474,11 +475,13 @@ Error: User does not have CREATE permission on catalog 'aco'
 ```python
 # 1. Develop locally with DuckDB
 from aco.lake import DuckDBContext
+
 ctx_local = DuckDBContext(database="notebooks/aco.duckdb")
 results = execute(readmissions.pipeline, ctx_local)
 
 # 2. Deploy to Unity Catalog
 from aco.lake import IcebergContext
+
 ctx_unity = IcebergContext(
     catalog_uri="https://dbc-7474655000864661.cloud.databricks.com/api/2.1/unity-catalog/iceberg",
     warehouse="aco",