fix: RST indentation in changelog

CHANGES.txt

@@ -8,15 +8,21 @@
   See https://github.com/Pylons/substanced/pull/314
 
 - Drop old Python versions (< 3.8), add newer ones (up to 3.12).
-  - Remove all the "straddle" compatibility stuff FBO Python 2.7
-  - Pin pyramid < 2.0dev, until it can be reviewed in depth.
-  - Fix deprecation warnings from pyramid.
-  - Silence deprecation warnings related to pkg_resources.
-  - Make ``py.test`` the testrunner (to support the newer Python versions).
-  - Replace ``cryptacular`` with plain ``bcrypt`` (the ``enscons`` builder
-    that ``cryptacular`` needs barfs on Python 3.12).
   See: https://github.com/Pylons/substanced/pull/307
 
+- Remove all the "straddle" compatibility stuff FBO Python 2.7
+
+- Pin pyramid < 2.0dev, until it can be reviewed in depth.
+
+- Fix deprecation warnings from pyramid.
+
+- Silence deprecation warnings related to pkg_resources.
+
+- Make ``py.test`` the testrunner (to support the newer Python versions).
+
+- Replace ``cryptacular`` with plain ``bcrypt`` (the ``enscons`` builder
+  that ``cryptacular`` needs barfs on Python 3.12).
+
 - Override ``serialize`` for ``ReferenceIdSchemaNode``.
   See https://github.com/Pylons/substanced/pull/311