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

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https://hg.mozilla.org/integration/gaia-central/rev/162dfbf95b31
Author: Pavel Ivanov <pivanov@mozilla.com>
Desc: Merge pull request #21711 from pivanov/bug-1035729

Bug 1035729 - [Video] - remove unused images

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https://hg.mozilla.org/integration/gaia-central/rev/9adf0370de05
Author: Pavel Ivanov <pivanov@mozilla.com>
Desc: Bug 1035729 - [Video] - remove unused images

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https://hg.mozilla.org/integration/gaia-central/rev/1c166d7d1a34
Author: Zac <zcampbell@mozilla.com>
Desc: Merge pull request #20015 from zacc/bug_1020166

Bug 1020166 - Update python IMEI tests to cope with 2 IMEI on Flame

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https://hg.mozilla.org/integration/gaia-central/rev/2b6d55eef4fa
Author: Zac <zcampbell@mozilla.com>
Desc: Bug 1020166 - Update pytest_MMI to cope with 2 IMEI on Flame
Bumping manifests a=b2g-bump