documentation

Pull request #3335: Feature/ZBXNEXT-7744 7.4 D

Merge in WEB/documentation from feature/ZBXNEXT-7744-7.4-D to release/7.4

* commit 'dbd6ec74d21b8a80e3c66940a6c69ecadcafc240':
  ZBXNEXT-7744 fixed a typo.
  ZBXNEXT-7744 fixed a what's new entry and a comment.
  ZBXNEXT-7744 added a what's new entry.
  ZBXNEXT-7744 added new parameters and comments cell content for Redis.
  ZBXNEXT-7744 formatting.