Merge branch '5.1' into 5.2

* 5.1:
  µCS fix
  CS fix
  CS fix
  [travis] use PHP 8.0 to patch return types and run deps=low
  Add me as a Notifier code owner
  Update sl_SI translations
  Don't trigger deprecation for deprecated aliases pointing to deprecated definitions
  [HttpFoundation] use atomic writes in MockFileSessionStorage
  Make EmailMessage & SmsMessage transport nullable
  remove unused argument
  [DI] fix param annotation
  [Config] Add \Symfony\Component\Config\Loader::load() return type
  Simplify PHP CS Fixer config
  Rename normalize param

Author: nicolas-grekas

composer.json

@@ -33,7 +33,7 @@
         "amphp/http-client": "^4.2.1",
         "amphp/http-tunnel": "^1.0",
         "amphp/socket": "^1.1",
-        "guzzlehttp/promises": "^1.3.1",
+        "guzzlehttp/promises": "^1.4",
         "nyholm/psr7": "^1.0",
         "php-http/httplug": "^1.0|^2.0",
         "psr/http-client": "^1.0",