fixed problem in compatibility definition

Author: samuraee

src/Adapter/Mellat.php

@@ -349,7 +349,7 @@ public function getGatewayReferenceId(): string
         return $this->RefId;
     }
 
-    public function afterVerify()
+    public function afterVerify(): bool
     {
         return $this->settleTransaction();
     }

src/Adapter/Saman.php

@@ -278,7 +278,7 @@ protected function getWSDL($type = null)
      * @return SoapClient
      * @throws SoapFault
      */
-    protected function getSoapClient($type = null)
+    protected function getSoapClient($type = null): SoapClient
     {
         return new SoapClient($this->getWSDL($type), $this->getSoapOptions());
     }