fix: do not change created_at on entity updates #2123

Job	Run time
integration (kong:1.4.3)	1m 59s
integration (kong:1.5.1)	1m 44s
integration (kong:2.0.5)	2m 22s
integration (kong:2.1.4)	1m 39s
integration (kong:2.2.2)	2m 0s
integration (kong:2.3.3)	1m 38s
integration (kong:2.4.1)	2m 7s
integration (kong:2.5.1)	1m 52s
integration (kong:2.6.0)	2m 17s
integration (kong:2.7)	1m 50s
integration (kong:2.8)	1m 47s
integration (kong:3.0)	1m 59s
integration (kong:3.1)	2m 18s
integration (kong:3.2)	2m 11s
integration (kong:3.3)	1m 51s
integration (kong/kong:master-alpine)	1m 54s
	31m 28s

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