[service] Tunnelbroker - Fix calling of removeMessageItem in DatabaseManager test

Summary:
This diff is a fix.
One occurrence of removeMessageItem(...) was missed to update due to the changes introduced in D4694. This diff fixes DatabaseManager tests to run without errors. At the moment DatabaseManager unit tests building fails with an error:

/transferred/test/DatabaseManagerTest.cpp: In member function 'virtual void DatabaseManagerTest_RemoveMessageItemsInBatch_Test::TestBody()':
/transferred/test/DatabaseManagerTest.cpp:387:45: error: no matching function for call to 'comm::network::database::DatabaseManager::removeMessageItem(std::string)'
  387 |       messageThirdToNotRemove.getMessageID());

Related linear task: ENG-1491

Test Plan:
Built and run unit tests for DatabaseManager in test/DatabaseManagerTest.cpp.
Tests were successfully built and run without errors.

Reviewers: karol, tomek

Reviewed By: tomek

Subscribers: ashoat, tomek, adrian, atul, abosh

Differential Revision: https://phab.comm.dev/D4739