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

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https://hg.mozilla.org/integration/gaia-central/rev/5c60ea756ecf
Author: Francisco Jordano <arcturus@ardeenelinfierno.com>
Desc: Merge pull request #20503 from arcturus/bug-1023911

Bug 1023911 - [Contacts] Investigate why integration test contacts_shortcuts_test.js is failing r=crdlc

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https://hg.mozilla.org/integration/gaia-central/rev/afe2b8bd82b3
Author: Francisco Jordano <fjordano@mozilla.com>
Desc: Bug 1023911 - [Contacts] Investigate why integration test contacts_shortcuts_test.js is failing

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https://hg.mozilla.org/integration/gaia-central/rev/a72969ba1f53
Author: Sergi Mansilla <sergi.mansilla@gmail.com>
Desc: Merge pull request #19989 from comoyo/bug-1020109

Bug 1020109 - Cell broadcast search list is not set correctly. r=arthurcc

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https://hg.mozilla.org/integration/gaia-central/rev/5e3f81eff8ae
Author: Kevin Simons <kevin@comoyo.com>
Desc: Bug 1020109 - Cell broadcast search list is not set correctly

The current code attempts to protect against empty objects incorrectly
since empty arrays are truthy in JavaScript. The result is empty objects
get passed to SettingsLock.set() which seems to break all subsequent
settings change observers.
Bumping manifests a=b2g-bump