Bump plopp from 24.9.1 to 24.9.2 in /requirements #342

Job	Run time
Formatting and static analysis	12s
Mantid tests	1m 42s
Tests (ubuntu-22.04, 3.10, py310) / package-test	22s
Tests (ubuntu-22.04, 3.10, py310) / test	1m 5s
docs / Build documentation	5m 21s
	8m 42s

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