Support `where.not` for `Rails/PluckInWhere` #30

Job	Run time
Check the oldest supported RuboCop version	25s
Ruby 2.7	35s
Check documentation syntax	14s
JRuby 9.4	2m 34s
Ruby 3.0	33s
Ruby 3.1	32s
Ruby 3.2	22s
Ruby head	25s
	5m 40s

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