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

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https://hg.mozilla.org/integration/gaia-central/rev/5a7ea9384090
Author: Francisco Jordano <arcturus@ardeenelinfierno.com>
Desc: Merge pull request #12988 from arcturus/bug-929071

Bug 929071 - [Contacts] Fix contacts merging unit test to ensure blob in |photo| field due to webidl change

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https://hg.mozilla.org/integration/gaia-central/rev/1153d14f5044
Author: Francisco Jordano <arcturus@ardeenelinfierno.com>
Desc: Bug 929071 - [Contacts] Fix contacts merging unit test to ensure blob in |photo| field due to webidl change

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https://hg.mozilla.org/integration/gaia-central/rev/5d0d3f3ae7c2
Author: Albert <acperez@tid.es>
Desc: Merge pull request #12934 from acperez/bug-927788

Bug 927788 - Add compatibility with NetworkStats API 2 for costcontrol.

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https://hg.mozilla.org/integration/gaia-central/rev/71a48ec35bce
Author: Albert <acperez@tid.es>
Desc: Bug 927788 - Add compatibility with NetworkStats API 2 for costcontrol