add type declaration to suspend the deprecated info message

[vikbert]

Added the explicit @return to suspend the deprecation info msg as showed in the following:

➜ dcphp bin/console c:c
Xdebug: [Step Debug] Could not connect to debugging client. Tried: host.docker.internal:9003 (through xdebug.client_host/xdebug.client_port) :-(

 // Clearing the cache for the dev environment with debug true

 [OK] Cache for the "dev" environment (debug=true) was successfully cleared.

2021-10-03T20:24:45+02:00 [info] User Deprecated: Method "Symfony\Component\HttpKernel\DataCollector\DataCollectorInterface::getName()" might add "string" as a native return type declaration in the future. Do the same in implementation "Doctrine\Bundle\MigrationsBundle\Collector\MigrationsCollector" now to avoid errors or add an explicit @return annotation to suppress this message.

[greg0ire]

Thanks @vikbert !

[vikbert]

thx for the quick code review 👍