Merge branch '4.4' into 5.2

* 4.4: [travis] use packagist API v2 [translation] Fix update existing key with existing +int-icu domain [Contracts] Fix branch name in README.md links

Author: nicolas-grekas

README.md

@@ -6,4 +6,4 @@ A set of abstractions extracted out of the Symfony components.
 Can be used to build on semantics that the Symfony components proved useful - and
 that already have battle tested implementations.
 
-See https://github.com/symfony/contracts/blob/master/README.md for more information.
+See https://github.com/symfony/contracts/blob/main/README.md for more information.