[OSGeo] #3052: Upgrade pretalx to latest version

[OSGeo]

#3052: Upgrade pretalx to latest version
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 Reporter:  robe      |      Owner:  sac@…
     Type:  task      |     Status:  new
 Priority:  normal    |  Milestone:  Sysadmin Contract 2023-I
Component:  SysAdmin  |   Keywords:
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 Current version is https://pretalx.com/p/news/releasing-pretalx-2023-1-3/

 Our last release was about a year ago.

 I'll test on staging first.
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Ticket URL: <https://trac.osgeo.org/osgeo/ticket/3052>
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