Merge branch '4.4' into 5.2

* 4.4:
  Replace "branch-version" by "versions" in composer.json
  Bump Symfony version to 4.4.20
  Update VERSION for 4.4.19
  Update CONTRIBUTORS for 4.4.19
  Update CHANGELOG for 4.4.19

Author: nicolas-grekas

composer.json

@@ -27,7 +27,6 @@
     },
     "minimum-stability": "dev",
     "extra": {
-        "branch-version": "2.3",
         "branch-alias": {
             "dev-main": "2.3-dev"
         },