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

========

https://hg.mozilla.org/integration/gaia-central/rev/3c687da8527e
Author: Gabriele Svelto <gsvelto@mozilla.com>
Desc: Merge pull request #31799 from gabrielesvelto/bug-1147735-deprecate-telephonycall-error

Bug 1147735 - Remove all uses of the deprecated TelephonyCall.onerror event r=drs

========

https://hg.mozilla.org/integration/gaia-central/rev/4318760448e6
Author: Gabriele Svelto <gsvelto@mozilla.com>
Desc: Bug 1147735 - Remove all uses of the deprecated TelephonyCall.onerror event r=drs

b2g/config/gaia.json

@@ -1,9 +1,9 @@
 {
     "git": {
-        "git_revision": "e42f7e9937b62f84d2baef547f5bd08e1a6ac44b", 
+        "git_revision": "4bf8e171a7ea3397901191a25765432594aaff2c", 
         "remote": "https://git.mozilla.org/releases/gaia.git", 
         "branch": ""
     }, 
-    "revision": "30bc42a5f94af00aa792b4c116428e2fb2b9c0f5", 
+    "revision": "3c687da8527e52c7c4450f948248ff42d2f1f8e7", 
     "repo_path": "integration/gaia-central"
 }