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

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https://hg.mozilla.org/integration/gaia-central/rev/a3a55ab202e6
Author: steveck-chung <schung@mozilla.com>
Desc: Merge pull request #16030 from steveck-chung/message-read-report

Bug 926852 - [Messages] Read receipts feature Gaia implementation. r=julienw , crh0716

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https://hg.mozilla.org/integration/gaia-central/rev/0f04f27a2398
Author: Steve Chung <schung@mozilla.com>
Desc: Bug 926852 - [Messages] Read receipts feature Gaia implementation
Bumping manifests a=b2g-bump