Bumping gaia.json for 3 gaia-central revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/15e0ed73da28
Author: Vivien Nicolas <21@vingtetun.org>
Desc: Bug 920561 - Ensure LazyLoader.load does not slow down app rendering. r=mbudzynski

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https://hg.mozilla.org/integration/gaia-central/rev/c02e61476598
Author: Vivien Nicolas <21@vingtetun.org>
Desc: Bug 920522 - Remove icc_helper.js from the Settings apps startup path. r=kaze

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https://hg.mozilla.org/integration/gaia-central/rev/a77b52ece92f
Author: Corey Frang <gnarf37@gmail.com>
Desc: Revert "Bug 917463 - [Clock] Implement scrolling inertia in inline time picker for Timers - r=jugglinmike"

This reverts commit 41f2c409c8baf9e5375ab0d41d0bbc3fe4ecf492.