Fix linting and unused import errors in blueprint tests

- Remove unused 'pathlib' and 'Blueprint' imports in test_client.py
- Apply black reformatting to test files
- Verified pass for black, ruff, isort, and mypy locally

Co-authored-by: rnovatorov <20299819+rnovatorov@users.noreply.github.com>

Author: google-labs-jules[bot]

tests/unit/test_http/test_api/test_blueprints/test_client.py

@@ -1,13 +1,12 @@
 """Unit tests for the Blueprints HTTP API client."""
 
-import pathlib
 from unittest.mock import AsyncMock, MagicMock
 
 import httpx
 import pytest
 
 import enapter
-from enapter.http.api.blueprints.blueprint import Blueprint, BlueprintView
+from enapter.http.api.blueprints.blueprint import BlueprintView
 
 
 @pytest.fixture