[DOC] update changelog (add browser removal to changes)

CHANGELOG.md

@@ -85,6 +85,7 @@ All changes are documented here in no particular order.
 - breaking: `env` is now frozen ([details](#28-env-is-now-frozen))
 - breaking: `renderToString` function on qweb has been removed ([details](#32-rendertostring-on-qweb-has-been-removed))
 - breaking: `debounce` utility function has been removed ([details](#34-debounce-utility-function-has-been-removed))
+- breaking: `browser` object has been removed ([details](#browser-object-has-been-removed))
 
 ## Details/Rationale/Migration
 
@@ -753,4 +754,12 @@ Otherwise, it will be escaped (just like `t-esc`).
 Migration: replace all `t-raw` uses by `t-out`, and uses the `markup` function
 to mark all the js values.
 
-Documentation: [Outputting data](doc/reference/templates.md#outputting-data)
+Documentation: [Outputting data](doc/reference/templates.md#outputting-data)
+
+## 39. `browser` object has been removed
+
+Rationale: the `browser` object caused more trouble than it was worth. Also, it
+seems like this should be done in user space, not at the framework level.  
+
+Migration: code should just be adapted to either use another browser object,
+or to use native browser function (and then, just mock them directly).