add comment explaining why HttpClient tests are run separately

Author: xabbuh

.github/workflows/windows.yml

@@ -110,6 +110,7 @@ jobs:
           Remove-Item -Path src\Symfony\Bridge\PhpUnit -Recurse
           mv src\Symfony\Component\HttpClient\phpunit.xml.dist src\Symfony\Component\HttpClient\phpunit.xml
           php phpunit src\Symfony --exclude-group tty,benchmark,intl-data,network,transient-on-windows || ($x = 1)
+          # HttpClient tests need to run separately, they block when run with other components' tests concurrently
           php phpunit src\Symfony\Component\HttpClient || ($x = 1)
 
           exit $x
@@ -123,6 +124,7 @@ jobs:
 
           Copy c:\php\php.ini-max c:\php\php.ini
           php phpunit src\Symfony --exclude-group tty,benchmark,intl-data,network,transient-on-windows || ($x = 1)
+          # HttpClient tests need to run separately, they block when run with other components' tests concurrently
           php phpunit src\Symfony\Component\HttpClient || ($x = 1)
 
           exit $x