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

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https://hg.mozilla.org/integration/gaia-2_0/rev/904f334ba62f
Author: Ryan VanderMeulen <ryanvm@gmail.com>
Desc: Merge pull request #26247 from gitmai/bug-1069157-pdfViewer-update-for-v2.0

Bug - 1069157 [PDF Viewer] Update viewer pdf for v2.0

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https://hg.mozilla.org/integration/gaia-2_0/rev/64f013af4546
Author: mai <mri@tid.es>
Desc: Bug - 1069157 [PDF Viewer] Update viewer pdf for v2.0
Bumping manifests a=b2g-bump