documentation

Pull request #3311: feature/ZBXNEXT-10222-7.5-D-v2

Merge in WEB/documentation from feature/ZBXNEXT-10222-7.5-D-v2 to release/8.0

* commit '89d881dcf24dba558fb0470bb12b8d874db16d70':
  [ZBXNEXT-10222] event cleanup by housekeeper for deleted triggers
  [ZBXNEXT-10222] optimized content