[ios] Update GN file after https://codereview.chromium.org/1574113003
[ios] Update GN file after https://codereview.chromium.org/1574113003

Review URL: https://codereview.chromium.org/1576393003

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#368878}

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