docs: point changelog section of readme to CHANGELOG file

README.md

@@ -34,10 +34,21 @@ Aldine is the default theme for the home page of [Pressbooks](https://pressbooks
 
 ## Changelog 
 
-### 1.9.0
+The changelog is [available on Github](https://github.com/pressbooks/pressbooks-aldine/blob/dev/CHANGELOG.md).
+
+
+## Upgrade Notice 
+
+
+### 1.8.3 
+
+- Aldine requires Pressbooks >= 5.17.0
+
+
+### 1.8.2 
+
+- Aldine requires Pressbooks >= 5.14.6
 
-* See: https://github.com/pressbooks/pressbooks-aldine/releases/tag/1.9.0
-* Full release history available at: https://github.com/pressbooks/pressbooks-aldine/releases
 
 ## Credits 
 

readme.txt

@@ -30,10 +30,8 @@ Aldine is the default theme for the home page of [Pressbooks](https://pressbooks
 3. Click Activate to use your new theme right away.
 
 == Changelog ==
-= 1.9.0 =
 
-* See: https://github.com/pressbooks/pressbooks-aldine/releases/tag/1.9.0
+The changelog is [available on Github](https://github.com/pressbooks/pressbooks-aldine/blob/dev/CHANGELOG.md).
-* Full release history available at: https://github.com/pressbooks/pressbooks-aldine/releases
 
 == Upgrade Notice ==