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

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https://hg.mozilla.org/integration/gaia-central/rev/27556b3448ae
Author: Jose M. Cantera <jmcanterafonseca@gmail.com>
Desc: Merge pull request #13622 from jmcanterafonseca/fix_regression_ds_api

Bug 937361 - [B2G][Contacts] Facebook contacts imported do not appear in...

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https://hg.mozilla.org/integration/gaia-central/rev/8354fe4d3aea
Author: Jose M. Cantera <jmcanterafonseca@gmail.com>
Desc: Bug 937361 - [B2G][Contacts] Facebook contacts imported do not appear in Contacts

b2g/config/gaia.json

@@ -1,4 +1,4 @@
 {
-    "revision": "5208f7d41f2f2ce88b8f14908af1ae5f2d9d9052", 
+    "revision": "27556b3448aeb9551a3c5fdab399778eb0fb97d6", 
     "repo_path": "/integration/gaia-central"
 }