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

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https://hg.mozilla.org/integration/gaia-central/rev/56cedb487649
Author: Gareth Aye <gaye@mozilla.com>
Desc: Merge pull request #15881 from millermedeiros/878476-week-view-two-month-end-wed

Bug 878476 - [calendar] week view: two month names in header despite all days of week belong to one month r=gaye

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https://hg.mozilla.org/integration/gaia-central/rev/3551437cb446
Author: Miller Medeiros <miller@millermedeiros.com>
Desc: Bug 878476 - [calendar] week view: two month names in header despite all days of week belong to one month r=gaye
Bumping manifests a=b2g-bump