fix reordering of slots function (#5840) #1

Job	Run time
Core Basic (18.x)	7m 20s
Core Basic (20.x)	6m 41s
Core Basic - Plone 5 (18.x)	6m 49s
Core Blocks (18.x)	8m 19s
Core Blocks - Listing (18.x)	5m 35s
Core Blocks (20.x)	7m 24s
Core Blocks - Listing (20.x)	5m 36s
Core Content (18.x)	3m 34s
Core Control Panels (18.x)	5m 37s
Core Content (20.x)	4m 34s
Core Control Panels (20.x)	4m 17s
Coresandbox (18.x)	4m 19s
Core Volto Slate (18.x)	7m 17s
Core Volto Slate (20.x)	7m 42s
Project Generator (18.x)	6m 42s
Multilingual (18.x)	4m 2s
Multilingual in Seamless Mode (18.x)	3m 42s
Project Generator (20.x)	6m 36s
Seamless Mode (18.x)	7m 4s
Working Copy (18.x)	3m 30s
	1h 56m 40s

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