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

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https://hg.mozilla.org/integration/gaia-2_1/rev/d537c2b9b433
Author: Luke Chang <lchang@mozilla.com>
Desc: Merge pull request #23304 from luke-chang/1056493_v1.4_contacts_to_homescreen_delay

Bug 1056493 - [Dolphin][Hamachi][v1.4]No icons show for several seconds when back to homescreen from contacts, r=alive
Bumping manifests a=b2g-bump