BUG/MINOR: http-request: fix enum for default-errorfile in return action #452

Job	Run time
HAProxy check commit message	0s
generate-models	1m 5s
generate-specification	32s
go mod tidy	20s
golangci-lint	1m 16s
Build	16s
lint-spec	6s
Tests	25s
e2e on HAProxy (2.1)	51s
e2e on HAProxy (2.2)	54s
e2e on HAProxy (2.3)	54s
e2e on HAProxy (2.4)	46s
e2e on HAProxy (2.5)	44s
e2e on HAProxy (2.6)	55s
e2e on HAProxy (2.7)	49s
e2e on HAProxy (2.8)	1m 5s
	10m 58s

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