Bumping gaia.json for 4 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/5b7dbc28c71b
Author: Ryan VanderMeulen <rvandermeulen@mozilla.com>
Desc: Merge pull request #18099 from Moz-TedC/bug-974794-vietnamese-ime-plus-telex

Bug 974794: Vietnamese IME. Incorporates Trung Ngo's Telex IME code.

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https://hg.mozilla.org/integration/gaia-central/rev/984e8613bbda
Author: Ted Clancy (:tedders1) <tclancy@mozilla.com>
Desc: Bug 974794: Vietnamese IME. Incorporates Trung Ngo's Telex IME code.

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https://hg.mozilla.org/integration/gaia-central/rev/13b6db7a3c0e
Author: Ryan VanderMeulen <rvandermeulen@mozilla.com>
Desc: Merge pull request #17553 from svic/Bug_969277

Bug 969277 - NFC pairing UI

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https://hg.mozilla.org/integration/gaia-central/rev/b561b527f1ce
Author: Arno Puder <arno@puder.org>
Desc: Bug 969277 - NFC pairing UI. r=alive
Bumping manifests a=b2g-bump