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

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https://hg.mozilla.org/integration/gaia-central/rev/87d4039f587f
Author: Germán Toro del Valle <gtorodelvalle@gmail.com>
Desc: Merge pull request #12621 from gtorodelvalle/contacts-bug-922083-unit-tests-for-duplicate-contact-details-reloaded

Contacts bug 922083 unit tests for duplicate contact details reloaded (r=jmcanterafonseca)

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https://hg.mozilla.org/integration/gaia-central/rev/35669903b494
Author: Germán Toro del Valle <gtorodelvalle@gmail.com>
Desc: Bug 922083 - [Contacts] Include unit tests to cover the presentation of the duplicate contact details overlay.

b2g/config/gaia.json

@@ -1,4 +1,4 @@
 {
-    "revision": "49e07ab5f7579d226e2258740d15f6311c917a8e", 
+    "revision": "87d4039f587f68d79969d13d56b59bcb31f0f1f6", 
     "repo_path": "/integration/gaia-central"
 }