documentation

Pull request #2138: ZBX-25639 changes in description of selected parameters.

Merge in WEB/documentation from feature/ZBX-25639-7.0-D to release/7.0

* commit 'fd8338817548a7db5373e84cc85afe032b07c83d':
  ZBX-25639 changed "Zabbix UI upgrade" to "Zabbix upgrade".
  ZBX-25639 unnecessary " removed.
  ZBX-25639 improvements in consistency and clarity.
  ZBX-25639 changes in description of selected parameters.