Bumping gaia.json for 1 gaia-central revision(s)

========

https://hg.mozilla.org/integration/gaia-central/rev/a183b055417d
Author: Rick Waldron <waldron.rick@gmail.com>
Desc: Bug 909641 - Re-enable SMS UI Thread Test (fails on CI)

Signed-off-by: Rick Waldron <waldron.rick@gmail.com>

b2g/config/gaia.json

@@ -1,4 +1,4 @@
 {
-    "revision": "4be7104e4a58b2fb67943c948f432f99e5135d68", 
+    "revision": "a183b055417d036b01e177750ab2ec6162d6fcd7", 
     "repo_path": "/integration/gaia-central"
 }