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

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https://hg.mozilla.org/integration/gaia-central/rev/151d5239446c
Author: Fernando Campo <fernando.campo@o2.com>
Desc: Merge pull request #13955 from fcampo/exported-label-translate-929552

Bug 936889 - Followup for bug 929552 - Sync string for exported contacts (r=pike)

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https://hg.mozilla.org/integration/gaia-central/rev/ebf7233783e7
Author: Fernando Campo <fernando.campo@o2.com>
Desc: Bug 936889 - Followup for bug 929552 - Sync string for exported contacts