internal/appsec: fix missing ResponseHeaderCopier call #2879

Job	Run time
Prepare Go modules cache	8s
Smoke Tests	0s
macos-latest (AppSec disabled)	1m 46s
windows-latest (AppSec disabled)	2m 43s
ubuntu-latest-16-cores (AppSec disabled)	1m 3s
macos-12 go1.22	6m 41s
macos-12 go1.21	6m 35s
macos-14 go1.22	3m 8s
macos-14 go1.21	4m 0s
linux/amd64 golang:1.22-bookworm	1m 28s
linux/arm64 golang:1.22-bookworm	2m 54s
linux/amd64 golang:1.22-bullseye	1m 27s
linux/arm64 golang:1.22-bullseye	3m 0s
linux/amd64 golang:1.22-alpine	1m 24s
linux/arm64 golang:1.22-alpine	2m 37s
linux/amd64 golang:1.21-bookworm	1m 25s
linux/arm64 golang:1.21-bookworm	2m 56s
linux/amd64 golang:1.21-bullseye	1m 26s
linux/arm64 golang:1.21-bullseye	2m 55s
linux/amd64 golang:1.21-alpine	1m 21s
linux/arm64 golang:1.21-alpine	3m 0s
	51m 57s

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