Bumping gaia.json for 1 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/777154ac05c8
Author: Zac <zcampbell@mozilla.com>
Desc: Revert "Bug 1000334 - Adjust b2g_start to work for v1.3 as well"

This reverts commit 910affc8410e75c913f3003e3891197309237b08.
Bumping manifests a=b2g-bump