Bumping gaia.json for 2 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/e3956f470dd9
Author: Jared Hirsch <ohai@6a68.net>
Desc: Merge pull request #20774 from 6a68/bug-1027950-settings-fmd-onerror-handlers

Bug 1027950 - [Settings][Find My Device] Do not attach handlers inside onerror callback

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https://hg.mozilla.org/integration/gaia-central/rev/0b6126d42d3c
Author: Jared Hirsch <ohai@6a68.net>
Desc: Bug 1027950 - Correctly initialize find my device settings panel. r=arthurcc

    * Do not attach handlers inside onerror callback.
    * Disable fmd login button until watch fires.
    * Add tests.
Bumping manifests a=b2g-bump