fix(deps): remove unmaintained deprecation package, inline stdlib replacement

The `deprecation` package (>=2.1.0,<3.0.0) has had no release since 2019
and is flagged as a security / maintenance risk by dependency scanners.
The package was only used in one file (`weaviate/collections/batch/client.py`)
to add docstring notes and emit `DeprecationWarning` at call time.

This PR removes the external dependency and replaces it with an equivalent
`docstring_deprecated` helper implemented entirely with stdlib (`functools`,
`warnings`).  The public behaviour is unchanged:

* The function docstring gets a `.. deprecated::` RST prefix.
* Calling the function emits a :class:`DeprecationWarning`.

The `typing_extensions.deprecated` import (already present) is kept because
it provides static analysis / IDE warnings via the `__deprecated__` attribute.

Fixes #1998

Signed-off-by: NIK-TIGER-BILL <nik.tiger.bill@github.com>

Author: NIK-TIGER-BILL

setup.cfg

@@ -40,7 +40,6 @@ install_requires =
     pydantic>=2.12.0,<3.0.0
     grpcio>=1.59.5,<1.80.0
     protobuf>=4.21.6,<7.0.0
-    deprecation>=2.1.0,<3.0.0
 python_requires = >=3.10
 
 [options.extras_require]

weaviate/collections/batch/client.py

@@ -1,9 +1,43 @@
 from concurrent.futures import ThreadPoolExecutor
 from typing import TYPE_CHECKING, Optional, Type, Union
 
-from deprecation import deprecated as docstring_deprecated
+import functools
+import warnings as _warnings
+from typing import Callable
+
 from typing_extensions import deprecated as typing_deprecated
 
+
+def docstring_deprecated(details: str = "", deprecated_in: str = "", **_kwargs: object) -> Callable:
+    """Replacement for ``deprecation.deprecated`` that uses only stdlib.
+
+    The ``deprecation`` package has not been maintained since 2019 and is
+    flagged as a security risk by several dependency scanners.  This
+    in-module helper replicates the behaviour we need:
+
+    1. Prepend a ``.. deprecated::`` note to the docstring.
+    2. Emit a :class:`DeprecationWarning` at call time.
+    """
+
+    def decorator(func: Callable) -> Callable:
+        docstring = func.__doc__ or ""
+        note = f".. deprecated:: {deprecated_in}\n   {details}\n\n" if deprecated_in else ""
+        func.__doc__ = note + docstring
+
+        @functools.wraps(func)
+        def wrapper(*args: object, **kwargs: object) -> object:
+            _warnings.warn(
+                f"{func.__qualname__} is deprecated since {deprecated_in}. {details}",
+                DeprecationWarning,
+                stacklevel=2,
+            )
+            return func(*args, **kwargs)
+
+        wrapper.__doc__ = func.__doc__
+        return wrapper
+
+    return decorator
+
 from weaviate.collections.batch.async_ import _BatchBaseAsync
 from weaviate.collections.batch.base import (
     _BatchBase,