fix: use replace deprecated custom json serialization with default pydantic v2 model_config (#501)

## Issue
#474 

## What?
removes the json_loads and json_dumps parameters from the ConfigDict and uses default model_config

## Why?
it is no longer supported by Pydantic V2

Author: anayeaye

stac_api/runtime/src/render.py

@@ -3,13 +3,7 @@
 from typing import Any, Dict, List, Optional
 from urllib.parse import urlencode
 
-import orjson
-from pydantic import BaseModel, ConfigDict
-
-
-def orjson_dumps(v: Dict[str, Any], *args: Any, default: Any) -> str:
-    """orjson.dumps returns bytes, to match standard json.dumps we need to decode."""
-    return orjson.dumps(v, default=default).decode()
+from pydantic import BaseModel
 
 
 def get_param_str(params: Dict[str, Any]) -> str:
@@ -53,8 +47,6 @@ def get_render_params(self) -> str:
         params = self.render_params.copy()
         return f"{get_param_str(params)}"
 
-    model_config = ConfigDict(json_loads=orjson.loads, json_dumps=orjson_dumps)
-
 
 def get_render_config(render_params) -> RenderConfig:
     """This is a placeholder for what may be a more complex function in the future.