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

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https://hg.mozilla.org/integration/gaia-central/rev/cf6d955a1703
Author: Wilson Page <wilsonpage@me.com>
Desc: Merge pull request #22366 from wilsonpage/1015249

Bug 1015249 - [Purchased Media] Update to use gaia-header

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https://hg.mozilla.org/integration/gaia-central/rev/cebe4ac014b7
Author: Wilson Page <wilsonpage@me.com>
Desc: Bug 1015249 - [Purchased Media] Update to use gaia-header
Bumping manifests a=b2g-bump