Agent: fix ICredentialCollector return type-hint

monkey/infection_monkey/credential_collectors/i_credential_collector.py

@@ -1,9 +1,10 @@
 from abc import ABC, abstractmethod
+from typing import List
 
 from .credentials import Credentials
 
 
 class ICredentialCollector(ABC):
     @abstractmethod
-    def collect_credentials(self) -> Credentials:
+    def collect_credentials(self) -> List[Credentials]:
         pass