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

========

https://hg.mozilla.org/integration/gaia-central/rev/87410a6c959a
Author: Cristian Rodriguez <crdlc@tid.es>
Desc: Merge pull request #13656 from crdlc/bug-938043

Bug 938043 - [Download Manager] Refine the shared component DownloadUI

========

https://hg.mozilla.org/integration/gaia-central/rev/0184baca2ac9
Author: crdlc <crdlc@tid.es>
Desc: Bug 938043 - [Download Manager] Refine the shared component DownloadUI