BUG/MINOR: http-request: fix enum for default-errorfile in return action #450

Job	Run time
HAProxy check commit message	0s
generate-models	1m 28s
generate-specification	48s
Build	26s
lint-spec	9s
go mod tidy	11s
golangci-lint	1m 34s
Tests	2m 39s
e2e on HAProxy (2.1)	41s
e2e on HAProxy (2.2)	41s
e2e on HAProxy (2.3)	41s
e2e on HAProxy (2.4)	41s
e2e on HAProxy (2.5)	40s
e2e on HAProxy (2.6)	52s
e2e on HAProxy (2.7)	39s
e2e on HAProxy (2.8)	46s
	12m 56s

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