fix(helm-e2e): read default gateway from /proc/net/route, not iproute2 #7

Job	Run time
Resolve PR metadata	7s
build-supervisor / Resolve build plan	3s
build-gateway / Resolve build plan	3s
build-supervisor / Rust sandbox (amd64) / sandbox (amd64)	2m 38s
build-gateway / Rust gateway (amd64) / gateway (amd64)	4m 13s
build-supervisor / Build supervisor (amd64)	1m 25s
build-gateway / Build gateway (amd64)	1m 26s
build-supervisor / Merge ${{ inputs.component }} manifest	0s
Helm E2E (rust)	1m 14s
Helm E2E (python)	1m 25s
build-gateway / Merge ${{ inputs.component }} manifest	0s
	12m 34s

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