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

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https://hg.mozilla.org/integration/gaia-central/rev/a0a462639938
Author: Anthony Ricaud <anthony@ricaud.me>
Desc: Revert "Merge pull request #23029 from yurenju/app-makefile-3"

This reverts commit 7855a89bc5e17ecc62e377b1bb7aab83ce881bc3, reversing
changes made to 193e46e885a53adefd0346725b3fc9b13e2dacae.

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https://hg.mozilla.org/integration/gaia-central/rev/ee4fc0734d42
Author: Ryan VanderMeulen <rvandermeulen@mozilla.com>
Desc: Merge pull request #22887 from tauzen/Bug971520-instantiable-manager

Bug 971520 - [System2] Instantiable NfcManager, r=alive

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https://hg.mozilla.org/integration/gaia-central/rev/7a0091ef0348
Author: Krzysztof Mioduszewski <kmioduszewski@gmail.com>
Desc: Bug 971520 - [System2] Instantiable NfcManager, r=alive
Bumping manifests a=b2g-bump