geckodriver: mention change to capabilities in changelog

Source-Repo: https://github.com/mozilla/geckodriver
Source-Revision: 6e6335a492e34ae5025bc16714ca38834f8e9f31

--HG--
extra : rebase_source : 364e05aaaf53d1a955a596994c668c4b1a82a8d0

testing/geckodriver/CHANGES.md

@@ -5,6 +5,7 @@ All notable changes to this program is documented in this file.
 ## Unreleased
 
 ### Changed
+- Accepted capabilities changed to a chromedriver-like dictionary of keys and values; this will cause `firefox_binary`, `firefox_args` and `firefox_profile` to stop working
 - Removed `--no-e10s` flag, and geckodriver will from now rely on the Firefox default multiprocessing settings (override using preferences)
 - Disable pop-up blocker in the default profile by @juangj