Bumping gaia.json for 1 gaia-central revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/448613ff1825
Author: Maciej Małecki <me@mmalecki.com>
Desc: Bug 923791 - [Messages] Fix SMS failure mocking on desktop r=rwaldron

https://bugzilla.mozilla.org/show_bug.cgi?id=923791

Reflect current `SmsRequest` API using `event.target.error`.

Rename `window.SMSDebugFail` to `window.MessagesDebugError` to reflect
how it's a string representing the error name.

Signed-off-by: Rick Waldron <waldron.rick@gmail.com>