Bumping gaia.json for 4 gaia-central revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/58804c21cd21
Author: Gareth Aye <gaye@mozilla.com>
Desc: Merge pull request #13532 from gaye/lightsofapollo-bug-832258-hide-sync-button

Bug 832258 - Hide sync button r=gaye

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https://hg.mozilla.org/integration/gaia-central/rev/5084eda4abd4
Author: Gareth Aye <gaye@mozilla.com>
Desc: Merge branch 'bug-832258-hide-sync-button' of https://github.com/lightsofapollo/gaia into lightsofapollo-bug-832258-hide-sync-button

Conflicts:
	apps/calendar/js/views/settings.js

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https://hg.mozilla.org/integration/gaia-central/rev/540bc492232a
Author: James Lal <james@lightsofapollo.com>
Desc: Show/hide sync button when account is added/removed

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https://hg.mozilla.org/integration/gaia-central/rev/a51cd8a2c98f
Author: James Lal <james@lightsofapollo.com>
Desc: Store.Account#syncableAccounts