documentation

Pull request #1340: feature/ZBX-22818-6.4-D: Added support for last_foreach in aggregate functions.

Merge in WEB/documentation from feature/ZBX-22818-6.4-D to release/6.4

* commit '5fe2466094f447a94dd0981a4a213c64fe2bf472':
  [ZBX-22818] Refined "What's new" entry to emphasize what's actually new
  [ZBX-22818] Added support for last_foreach in aggregate functions (updated "Aggregate functions" page)
  [ZBX-22818] Added support for last_foreach in aggregate functions (updated "What's new" page)