DDC-3778: [GH-1430] "INSTANCE OF" example doesn't match description.

[doctrinebot]

Jira issue originally created by user @doctrinebot:

This issue is created automatically through a Github pull request on behalf of michael-lavaveshkul:

Url: #1430

Message:

Just did a small change. The DQL is supposed to

[Query] for the staffs without getting any technicians

As it's currently written, it would select all Staff and the INSTANCE OF check would only test if they're Staff.

[doctrinebot]

Comment created by @doctrinebot:

A related Github Pull-Request [GH-1430] was assigned:
#1430

[doctrinebot]

Comment created by @doctrinebot:

A related Github Pull-Request [GH-1430] was merged:
#1430

[doctrinebot]

Issue was closed with resolution "Fixed"

[doctrinebot]

Comment created by @zeroedin-bill:

Backported to 2.5