[Plone-installers] Updated unified installer r3 for Plone 5.2.1

[T. K. N. <ng...@pl...>]

I updated the Plone 5.2.1 unified installer to r3 to include the waitress 1.4.3 pin and the 20200121 hotfix 1.1

https://community.plone.org/t/updated-unified-installer-r3-for-plone-5-2-1/11711