fix: hard-code khisto version

Otherwise, Sphinx cannot find the khisto package metadata, because
khisto itself is not installed.

Author: popescu-v

src/khisto/__init__.py

@@ -3,7 +3,6 @@
 # at https://spdx.org/licenses/BSD-3-Clause-Clear.html or see the "LICENSE" file for more details.
 
 import os
-from importlib.metadata import version
 from pathlib import Path
 import logging
 
@@ -14,7 +13,7 @@
 
 KHISTO_BIN_DIR = os.environ.get("KHISTO_BIN_DIR", "khisto")
 
-__version__ = version("khisto")
+__version__ = "0.1.0"
 
 from .array import histogram  # noqa: E402
 from .core import HistogramResult  # noqa: E402