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

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https://hg.mozilla.org/integration/gaia-central/rev/aa1e2bec7aab
Author: vingtetun <21@vingtetun.org>
Desc: Merge pull request #15928 from brendandahl/pdfjs-0.8.997

Bug 966865 - Update pdf.js to version 0.8.997.

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https://hg.mozilla.org/integration/gaia-central/rev/c5c69e7db367
Author: Brendan Dahl <brendan.dahl@gmail.com>
Desc: Bug 966865 - Update pdf.js to version 0.8.997.
Bumping manifests a=b2g-bump