Merge branch '7.1' into 7.2

* 7.1: (21 commits)
  [Serializer] [ObjectNormalizer] Use bool filter when FILTER_BOOL is set
  [HttpClient][Mailer] Revert "Let curl handle transfer encoding", use HTTP/1.1 for Mailgun
  Reviewed Catalan missing translations
  [AssetMapper] Upgrade importmap polyfill
  [HttpClient] Fix initializing InformationalChunk
  Fix typo: synchronous -> synchronously
  forward exceptions caught in the AbstractObjectNormalizer
  [Serializer] Check if exception message in test is correct
  [Serializer] Check if exception message in test is correct
  take the new DOM HTMLElement class into account
  Ibexa is sponsoring Symfony 5.4, thanks to them! \o/
  [FrameworkBundle] Fix warming up routes
  [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
  ...

Transport/MailgunHttpTransport.php

@@ -61,6 +61,7 @@ protected function doSendHttp(SentMessage $message): ResponseInterface
 
         $endpoint = \sprintf('%s/v3/%s/messages.mime', $this->getEndpoint(), urlencode($this->domain));
         $response = $this->client->request('POST', 'https://'.$endpoint, [
+            'http_version' => '1.1',
             'auth_basic' => 'api:'.$this->key,
             'headers' => $headers,
             'body' => $body->bodyToIterable(),