Revert "Change client __init__ to lazy import to avoid circular imports"

This reverts commit 5ac1b64.

src/promptflow-devkit/promptflow/client/__init__.py

@@ -3,21 +3,9 @@
 # ---------------------------------------------------------
 __path__ = __import__("pkgutil").extend_path(__path__, __name__)  # type: ignore
 
-
-_imported_attr = {}
-
-
 # control plane sdk functions
-# Use lazy import to avoid circular import
-# Circular path: PFClient -> UserAgent -> client._version -> client.__init__ -> PFClient
-def __getattr__(name):
-    if name in _imported_attr:
-        return _imported_attr[name]
-    if name in ["PFClient", "load_run", "load_flow"]:
-        from promptflow._sdk._load_functions import load_flow, load_run  # noqa: F401
-        from .._sdk._pf_client import PFClient  # noqa: F401
+from promptflow._sdk._load_functions import load_flow, load_run
 
-        _imported_attr[name] = locals()[name]
-        return _imported_attr[name]
+from .._sdk._pf_client import PFClient
 
-    raise AttributeError(f"module {__name__!r} has no attribute {name!r}")
+__all__ = ["PFClient", "load_run", "load_flow"]