Bump elliptic from 6.5.3 to 6.6.0 in /test/dockerfiles/webpack #661

Job	Run time
prepare (mainline)	36s
prepare (buildkit)	19s
prepare (desktop)	26s
validate (./hack/lint)	30s
validate (./hack/validate-vendor)	21s
test (mainline)	3m 40s
e2e (mainline, pip-youtube-dl, linux/arm/v7)	1m 31s
validate (./hack/install-and-test)	36s
test (buildkit)	37s
e2e (mainline, webpack, linux/arm/v7)	2m 5s
test (desktop)	9s
e2e (desktop, pip-youtube-dl, linux/arm/v7)	1m 29s
e2e (desktop, webpack, linux/arm/v7)	2m 3s
e2e (mainline, ejabberd, linux/arm64)	14m 8s
e2e (desktop, tini, linux/arm64, --rm)	37s
e2e (desktop, postgis, linux/arm64, -d --name postgis, postgis, UTC [1] LOG: database system is ...	47s
build (mainline)	1m 56s
build (buildkit)	33s
build (desktop)	1m 47s
	34m 10s

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