Dependabot: Remove deprecated `reviewers` config #4259

Job	Run time
Config export (ubuntu-latest, linked)	1m 6s
Config export (macos-latest, nightly-latest)	1m 3s
Config export (windows-latest, linked)	4m 4s
Config export (ubuntu-latest, nightly-latest)	1m 0s
Config export (macos-latest, linked)	1m 17s
Config export (windows-latest, nightly-latest)	4m 43s
	13m 13s

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