Bumping gaia.json for 4 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/b3bc7b2c5020
Author: autolander <bug.autolander@gmail.com>
Desc: Bug 1043903 - merge pull request #28458 from azasypkin:bug-1043903-integration-test-scroll to mozilla-b2g:master

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https://hg.mozilla.org/integration/gaia-central/rev/54af1eb8fa64
Author: Aleh Zasypkin <azasypkin@mozilla.com>
Desc: Bug 1043903 - [Messages][Tests] Add integration tests for the thread panel with a large number of messages. r=julien

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https://hg.mozilla.org/integration/gaia-central/rev/db4192b77d48
Author: autolander <bug.autolander@gmail.com>
Desc: Bug 1152073 - merge pull request #29598 from KevinGrandon:bug_1152073_system_dialog_style to mozilla-b2g:master

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https://hg.mozilla.org/integration/gaia-central/rev/3547cb16714b
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 1152073 - Update system dialog styles r=apastor

b2g/config/gaia.json

@@ -1,9 +1,9 @@
 {
     "git": {
-        "git_revision": "a7e198fb0aa004c5eebdf7f00a4431538f54f87d", 
+        "git_revision": "a8e4f95dce9db727dda5d408b038f97fb4296557", 
         "remote": "https://git.mozilla.org/releases/gaia.git", 
         "branch": ""
     }, 
-    "revision": "09ee05e26db9c5f021e2484e4a9a668da8e23007", 
+    "revision": "b3bc7b2c50201c1110e3f7157d6ed542e52d9355", 
     "repo_path": "integration/gaia-central"
 }