Fix event-loop-blocking time.sleep in async wait_for_weaviate (#2104)

The async ConnectionAsync.wait_for_weaviate startup-retry loop called
time.sleep(1), blocking the whole event loop for up to startup_period
seconds. Use await asyncio.sleep(1) so the loop stays responsive,
matching the async-sleep pattern already used elsewhere (retry.py,
export/executor.py). The synchronous wait_for_weaviate is unchanged.

Author: kratos0718

weaviate/connect/v4.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import asyncio
 import time
 from copy import copy
 from dataclasses import dataclass, field
@@ -1159,7 +1160,7 @@ async def wait_for_weaviate(self, startup_period: int) -> None:
                 ).raise_for_status()
                 return
             except (ConnectError, ReadError, TimeoutError, HTTPStatusError):
-                time.sleep(1)
+                await asyncio.sleep(1)
 
         try:
             (