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

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https://hg.mozilla.org/integration/gaia-central/rev/30a47d350e69
Author: Salvador de la Puente González <salva@unoyunodiez.com>
Desc: Merge pull request #11120 from leob2g/Bug_896848_Usage_App_Closing_When_Receive_a_Call

[CostControl] Bug_896848_Closing_Usage_app_after_call
r=lodr

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https://hg.mozilla.org/integration/gaia-central/rev/a6bccc065679
Author: sarath27.vs <sarath27.vs@lge.com>
Desc: Bug_896848_Closing_Usage_app_after_call

b2g/config/gaia.json

@@ -1,4 +1,4 @@
 {
-    "revision": "01f697002cd96fb89df23f19e532d472d48f9e7d", 
+    "revision": "30a47d350e69f4e642b11120f3a02e76bae031aa", 
     "repo_path": "/integration/gaia-central"
 }