Rename search_types to search_type to standardize to singular naming

Using singular names for other directories in application already
 - processor instead of processors
 - interface instead of interfaces

main.py

@@ -1,6 +1,6 @@
 from typing import Optional
 from fastapi import FastAPI
-from search_types import asymmetric
+from search_type import asymmetric
 import argparse
 import pathlib
 import uvicorn