Merge branch '6.4' into 7.0

* 6.4:
  [HttpClient][Mailer] Revert "Let curl handle transfer encoding", use HTTP/1.1 for Mailgun
  Reviewed Catalan missing translations
  [AssetMapper] Upgrade importmap polyfill
  Fix typo: synchronous -> synchronously
  [Serializer] Check if exception message in test is correct
  Ibexa is sponsoring Symfony 5.4, thanks to them! \o/
  [VarDumper] Fix `FFICaster` test to be platform-adaptable
  [String] Add `alias` case to `EnglishInflector`
  [FrameworkBundle] Throw runtime exception when trying to use asset-mapper while http-client is disabled
  [SecurityBundle] Remove unused memory users’ `name` attribute from the XSD
  [VarExporter] generate __doUnserialize() method in ProxyHelper::generateLazyProxy()
  Double check if pcntl function exists
  Add additional headers in Scaleway bridge
  [VarDumper] Fix FFI caster test
  [DependencyInjection] Add test coverage for `AutowireCallable::buildDefinition()`

MailerInterface.php

@@ -15,7 +15,7 @@
 use Symfony\Component\Mime\RawMessage;
 
 /**
- * Interface for mailers able to send emails synchronous and/or asynchronous.
+ * Interface for mailers able to send emails synchronously and/or asynchronously.
  *
  * Implementations must support synchronous and asynchronous sending.
  *