Bump to 9.0.1 final

CHANGES.rst

@@ -1,5 +1,5 @@
-Release 9.0.1 (in development)
-==============================
+Release 9.0.1 (released Dec 01, 2025)
+=====================================
 
 Bugs fixed
 ----------

sphinx/__init__.py

@@ -22,12 +22,12 @@ __display_version__: Final = __version__  # used for command line version
 #:
 #: .. versionadded:: 1.2
 #:    Before version 1.2, check the string ``sphinx.__version__``.
-version_info: Final = (9, 0, 1, 'beta', 0)
+version_info: Final = (9, 0, 1, 'final', 0)
 
 package_dir: Final = _StrPath(__file__).resolve().parent
 del _StrPath
 
-_in_development = True
+_in_development = False
 if _in_development:
     # Only import subprocess if needed
     import subprocess