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

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https://hg.mozilla.org/integration/gaia-central/rev/d54ed844691d
Author: Zac <zcampbell@mozilla.com>
Desc: Bug 1038698 - Disable intermittent test_a11y_utility_tray_visibility.py for TBPL

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https://hg.mozilla.org/integration/gaia-central/rev/bf5dc1f3ba5d
Author: Dale Harvey <dale@arandomurl.com>
Desc: Bug 1033487 - Wait for homeIcons init before unpinning. r=kgrandon
Bumping manifests a=b2g-bump