Fix lambda return type inference (#20457)

Some compilers (some ARM-based Linux compilers) have difficulty
inferring the return type of lambdas that don't explicitly state their
return type. This causes issues when passing lambdas as arguments into
functions that expect a specific function signature.

This fixes this specific instance in CASEServer that has this problem.

src/protocols/secure_channel/CASEServer.cpp

@@ -162,7 +162,7 @@ void CASEServer::OnSessionEstablishmentError(CHIP_ERROR err)
     // from a SessionDelegate::OnSessionReleased callback. Schedule the preparation as an async work item.
     //
     mSessionManager->SystemLayer()->ScheduleWork(
-        [](auto * systemLayer, auto * appState) {
+        [](auto * systemLayer, auto * appState) -> void {
             CASEServer * _this = static_cast<CASEServer *>(appState);
             _this->PrepareForSessionEstablishment();
         },