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

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https://hg.mozilla.org/integration/gaia-central/rev/12e1f6c57107
Author: Ryan VanderMeulen <rvandermeulen@mozilla.com>
Desc: Merge pull request #14676 from TheoChevalier/setringtone-reused-strings

Bug 950469 - [Setringtone][l12y] 'Set as ringtone' string is reused on t...

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https://hg.mozilla.org/integration/gaia-central/rev/3227446feb9a
Author: TheoChevalier <theo.chevalier11@gmail.com>
Desc: Bug 950469 - [Setringtone][l12y] 'Set as ringtone' string is reused on title and button

b2g/config/gaia.json

@@ -1,4 +1,4 @@
 {
-    "revision": "098f99ff8b33f0436b7be27624fb874d63112336", 
+    "revision": "12e1f6c571078c0e37ef955c2b6c06f164c9eb3d", 
     "repo_path": "/integration/gaia-central"
 }