Bump version and update changelog

Author: lafrech

CHANGELOG.rst

@@ -1,6 +1,14 @@
 Changelog
 ---------
 
+6.8.4 (2025-09-22)
+******************
+
+Bug fixes:
+
+- Set ``TimeDelta`` field type according to ``serialization_type`` (:pr:`990`).
+  Thanks :user:`LewisHaley` for the PR.
+
 6.8.3 (2025-09-07)
 ******************
 

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "apispec"
-version = "6.8.3"
+version = "6.8.4"
 description = "A pluggable API specification generator. Currently supports the OpenAPI Specification (f.k.a. the Swagger specification)."
 readme = "README.rst"
 license = { file = "LICENSE" }