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

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https://hg.mozilla.org/integration/gaia-central/rev/b8c327a878e0
Author: Marina <marina.rodrigueziglesias@telefonica.com>
Desc: Merge pull request #25547 from gitmai/bug-1069157-pdfViewer-update-pdf.js

Bug 1069157 - [PDF Viewer] update pdf.js in Gaia
r=yuri

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https://hg.mozilla.org/integration/gaia-central/rev/8ad666435350
Author: mai <mri@tid.es>
Desc: Bug 1069157 - [PDF Viewer] update pdf.js in Gaia
Bumping manifests a=b2g-bump