Bumping gaia.json for 4 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/546543ac49c9
Author: George <georgeiscoming@gmail.com>
Desc: Merge pull request #21150 from cctuan/1031123

Bug 1031123 - Using sdk/system/child_process for utils.Commander

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https://hg.mozilla.org/integration/gaia-central/rev/8e2f60d59e30
Author: cctuan <georgeiscoming@gmail.com>
Desc: Bug 1031123 - Using sdk/system/child_process for utils.Commander

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https://hg.mozilla.org/integration/gaia-central/rev/71a5b3bc9d60
Author: lissyx <lissyx+github@lissyx.dyndns.org>
Desc: Merge pull request #21568 from lissyx/bug1030063

Bug 1030063 - Use Notification API for CaptivePortal r=alive

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https://hg.mozilla.org/integration/gaia-central/rev/e6b309cb8da8
Author: Alexandre Lissy <lissyx+github@lissyx.dyndns.org>
Desc: Bug 1030063 - Use Notification API for CaptivePortal
Bumping manifests a=b2g-bump