Fix CI: Make pgvector an optional dependency, fix SQL injection and type errors

Co-Authored-By: Joe Moura <joao@crewai.com>

tests/knowledge/pgvector_knowledge_storage_test.py

@@ -1,6 +1,4 @@
-import os
 import pytest
-from typing import Dict, Any, List
 from unittest.mock import patch, MagicMock
 
 from crewai.knowledge.storage.pgvector_knowledge_storage import PGVectorKnowledgeStorage