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

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https://hg.mozilla.org/integration/gaia-central/rev/9ec972faf1cb
Author: Anthony Ricaud <anthony@ricaud.me>
Desc: Merge pull request #24705 from Rik/short-voicemail-831974

Bug 831974 - User has to press 1 for a long time before Voicemail is rea... r=drs

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https://hg.mozilla.org/integration/gaia-central/rev/25cdbe7753af
Author: Anthony Ricaud <anthony@ricaud.me>
Desc: Bug 831974 - User has to press 1 for a long time before Voicemail is reached

b2g/config/gaia.json

@@ -4,6 +4,6 @@
         "remote": "", 
         "branch": ""
     }, 
-    "revision": "3cd66e8297438593b5e1f4ed87ac4c5c8a1daa4a", 
+    "revision": "9ec972faf1cb7b31deab6cee2fbd6ec8f95022d8", 
     "repo_path": "/integration/gaia-central"
 }