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

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https://hg.mozilla.org/integration/gaia-central/rev/48fc35132326
Author: Marcus Cavanaugh <m@mcav.com>
Desc: Merge pull request #23976 from mcav/attachzero

Bug 1063310 - [email] When sending multiple attachments, all but the fir...

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https://hg.mozilla.org/integration/gaia-central/rev/92231f1be54c
Author: Marcus Cavanaugh <m@mcav.com>
Desc: Bug 1063310 - [email] When sending multiple attachments, all but the first are sent as zero-byte attachments. r=asuth
Bumping manifests a=b2g-bump