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

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https://hg.mozilla.org/integration/gaia-central/rev/5b155607f9eb
Author: Salvador de la Puente González <salva@unoyunodiez.com>
Desc: Merge pull request #11843 from lodr/bug-910170-disable-action-when-no-selected

Bug 910170 - Disable action button when no contact is selected
r=arcturus

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https://hg.mozilla.org/integration/gaia-central/rev/6ec4c6d9f243
Author: lodr <salva@unoyunodiez.com>
Desc: Bug 910170 - Disable action button when no contact is selected

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https://hg.mozilla.org/integration/gaia-central/rev/ca612032b298
Author: Cristian Rodriguez <crdlc@tid.es>
Desc: Merge pull request #11862 from crdlc/bug-908561

Bug 908561 - [Buri] "Add to home screen" wont dismiss the iframe when adding a bookmark, adding a e.me app

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https://hg.mozilla.org/integration/gaia-central/rev/16f28a1570b2
Author: crdlc <crdlc@tid.es>
Desc: Bug 908561 - [Buri] Add to home screen wont dismiss the iframe when adding a bookmark, adding a e.me app

b2g/config/gaia.json

@@ -1,4 +1,4 @@
 {
-    "revision": "d9f759cc10938a3caa252e96420531bbb6d6cab3", 
+    "revision": "5b155607f9eb535a61093e6259394f3bae4e4d48", 
     "repo_path": "/integration/gaia-central"
 }