Userland: Make IPC handlers return void if they don't have any outputs

Author: https://github.com/gunnarbeutner
Commit: 889359b6f9
Pull-request: https://github.com/SerenityOS/serenity/pull/6805
Reviewed-by: https://github.com/alimpfard

Userland/Libraries/LibProtocol/RequestClient.cpp

@@ -83,13 +83,11 @@ void RequestClient::handle(const Messages::RequestClient::HeadersBecameAvailable
     }
 }
 
-Messages::RequestClient::CertificateRequestedResponse RequestClient::handle(const Messages::RequestClient::CertificateRequested& message)
+void RequestClient::handle(const Messages::RequestClient::CertificateRequested& message)
 {
     if (auto request = const_cast<Request*>(m_requests.get(message.request_id()).value_or(nullptr))) {
         request->did_request_certificates({});
     }
-
-    return {};
 }
 
 }