docs: document deletion of `databases` directory (#45412)

docs/breaking-changes.md

@@ -226,6 +226,14 @@ win.webContents.navigationHistory.canGoToOffset()
 win.webContents.navigationHistory.goToOffset(index)
 ```
 
+### Behavior changed: Directory `databases` in `userData` will be deleted
+
+If you have a directory called `databases` in the directory returned by
+`app.getPath('userData')`, it will be deleted when Electron 32 is first run.
+The `databases` directory was used by WebSQL, which was removed in Electron 31.
+Chromium now performs a cleanup that deletes this directory. See
+[issue #45396](https://github.com/electron/electron/issues/45396).
+
 ## Planned Breaking API Changes (31.0)
 
 ### Removed: `WebSQL` support