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

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https://hg.mozilla.org/integration/gaia-central/rev/1bfa9e10dc2b
Author: Salvador de la Puente González <salva@unoyunodiez.com>
Desc: Merge pull request #12387 from leob2g/Bug_915992_Changing_default_configuration_to_Postpaid

[Cost Control] Bug_915992_Changing_default_config_to_Postpaid r=lodr

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https://hg.mozilla.org/integration/gaia-central/rev/ebc57c722136
Author: sarath27.vs <sarath27.vs@lge.com>
Desc: Changing default config to Postpaid

b2g/config/gaia.json

@@ -1,4 +1,4 @@
 {
-    "revision": "0964e9ebb8516422efba3538dff3535a23d1fa5f", 
+    "revision": "1bfa9e10dc2badf7b2ad137e534f2f75c39923b3", 
     "repo_path": "/integration/gaia-central"
 }