Merge branch '5.1' into 5.2

* 5.1:
  Use more explicit variable name
  Fix wrong comment about SES region
  [Mailer] [Sendgrid] Use $scheme variable to stay consistent
  [Mailer] [Amazon] Fix @param annotation
  [Mailer] Rename testsuites
  Remove void return type from test methods
  Remove void return type from test methods
  [Notifier] Remove void return type from test methods

Author: derrabus

Tests/DependencyInjection/FrameworkExtensionTest.php

@@ -1578,7 +1578,7 @@ public function provideMailer(): array
     /**
      * @dataProvider provideMailer
      */
-    public function testMailer(string $configFile, array $expectedTransports): void
+    public function testMailer(string $configFile, array $expectedTransports)
     {
         $container = $this->createContainerFromFile($configFile);
 
@@ -1599,14 +1599,14 @@ public function testMailer(string $configFile, array $expectedTransports): void
         $this->assertCount(3, $h->getMethodCalls());
     }
 
-    public function testMailerWithDisabledMessageBus(): void
+    public function testMailerWithDisabledMessageBus()
     {
         $container = $this->createContainerFromFile('mailer_with_disabled_message_bus');
 
         $this->assertNull($container->getDefinition('mailer.mailer')->getArgument(1));
     }
 
-    public function testMailerWithSpecificMessageBus(): void
+    public function testMailerWithSpecificMessageBus()
     {
         $container = $this->createContainerFromFile('mailer_with_specific_message_bus');