receive/multitsdb: do not delete not uploaded blocks #13642

Job	Run time
Go build for different platforms	8m 23s
Thanos end-to-end tests (8, 0)	4m 42s
Thanos end-to-end tests (8, 1)	4m 29s
Linters (Static Analysis) for Go	1m 17s
Thanos end-to-end tests (8, 2)	4m 20s
Thanos end-to-end tests (8, 3)	3m 52s
Thanos end-to-end tests (8, 4)	6m 34s
Thanos end-to-end tests (8, 5)	3m 59s
Thanos end-to-end tests (8, 6)	4m 36s
Thanos end-to-end tests (8, 7)	3m 58s
	46m 10s

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