Revert async client commits from master

These changes should go through a PR for review, not directly on master.
Reverts commits c13a241, 4278071, a3f5be0, 14eb635.
The work is preserved on the async-client branch.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: gijzelaerr

snap7/__init__.py

@@ -8,7 +8,6 @@
 from importlib.metadata import version, PackageNotFoundError
 
 from .client import Client
-from .async_client import AsyncClient
 from .server import Server
 from .partner import Partner
 from .logo import Logo
@@ -17,7 +16,6 @@
 
 __all__ = [
     "Client",
-    "AsyncClient",
     "Server",
     "Partner",
     "Logo",