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

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https://hg.mozilla.org/integration/gaia-1_4/rev/505269afccfe
Author: Justin D'Arcangelo <justindarc@gmail.com>
Desc: Merge pull request #18462 from justindarc/bug993686

Bug 993686 - [B2G][Camera] - Tapping repeatedly on capture button while ...

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https://hg.mozilla.org/integration/gaia-1_4/rev/5851080e0a38
Author: Douglas Sherk <github@sherk.me>
Desc: Merge pull request #17956 from DouglasSherk/965854-voicemail-sim-indicator

Bug 965854 - [DSDS][System] Display SIM indication in voicemail notification. r=etienne
Conflicts:
	apps/system/index.html
Bumping manifests a=b2g-bump