chore: update changelog and release instructions

Author: maartenbreddels

docs/source/changelog.md

@@ -4,6 +4,14 @@ ipywidgets changelog
 A summary of changes in ipywidgets. For more detailed information, see the issues and pull requests for the appropriate milestone on [GitHub](https://github.com/jupyter-widgets/ipywidgets).
 
 
+7.7.4
+-----
+
+Highlights include
+
+ - (backport) Fix: add grey as valid color [#3671](https://github.com/jupyter-widgets/ipywidgets/pull/3671) 
+ - (backport) Fix: use of structuredClone allows for binary traits out of the box [#3689](https://github.com/jupyter-widgets/ipywidgets/pull/3689)
+ - (backport) Fix: support the comm package [#3533](https://github.com/jupyter-widgets/ipywidgets/pull/3533)
 
 7.7.3
 -----

docs/source/dev_release.md

@@ -10,7 +10,7 @@ conda deactivate
 conda remove --all -y -n releasewidgets
 rm -rf ipywidgets
 
-conda create -c conda-forge --override-channels -y -n releasewidgets notebook "nodejs==16.*" "yarn<2" twine jupyterlab=3 jupyter-packaging jq python==3.8
+conda create -c conda-forge --override-channels -y -n releasewidgets notebook "nodejs==16.*" "yarn<2" twine jupyterlab=3 jupyter-packaging jq python==3.9
 conda activate releasewidgets
 
 git clone [email protected]:jupyter-widgets/ipywidgets.git