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

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https://hg.mozilla.org/integration/gaia-central/rev/a554876c79ae
Author: Gareth Aye <gaye@mozilla.com>
Desc: Merge pull request #15335 from millermedeiros/flaky-day-view-header-test

Bug 959901 - [Calendar][Integration Test] "day_view_test.js" is permared r=gaye

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https://hg.mozilla.org/integration/gaia-central/rev/414590d7eaf8
Author: millermedeiros <miller@millermedeiros.com>
Desc: bug 959901 - [calendar][integration test] "day_view_test.js" is permared
Bumping manifests a=b2g-bump