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

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https://hg.mozilla.org/integration/gaia-central/rev/b4915d85ad52
Author: Aleh Zasypkin <aleh.zasypkin@gmail.com>
Desc: Merge pull request #20797 from azasypkin/bug-1012663-csp-compliance-back

Bug 1012663 - [SMS] Remove inline style for CSP compliance. r=julienw

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https://hg.mozilla.org/integration/gaia-central/rev/738c3159ec5e
Author: Aleh Zasypkin <azasypkin@mozilla.com>
Desc: Bug 1012663 - [SMS] Remove inline style for CSP compliance. r=julienw
Bumping manifests a=b2g-bump