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

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https://hg.mozilla.org/integration/gaia-central/rev/a378b9d1db68
Author: Wilson Page <wilsonpage@me.com>
Desc: Merge pull request #26359 from wilsonpage/1102138

Bug 1102138 - [gaia-header] Should no longer reverse content in RTL mode

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https://hg.mozilla.org/integration/gaia-central/rev/a628ca8b272e
Author: Wilson Page <wilsonpage@me.com>
Desc: Bug 1102138 - [gaia-header] Should no longer reverse content in RTL mode
Bumping manifests a=b2g-bump