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

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https://hg.mozilla.org/integration/gaia-central/rev/12e4908f7b76
Author: Julien Wajsberg <felash@gmail.com>
Desc: Merge pull request #33394 from julienw/less-flickering

Bug 1228352 - [Messages] Reduce the flickering happening in activitie…

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https://hg.mozilla.org/integration/gaia-central/rev/7690d179844d
Author: Julien Wajsberg <felash@gmail.com>
Desc: Bug 1228352 - [Messages] Reduce the flickering happening in activities, and streamline animations r=azasypkin

b2g/config/gaia.json

@@ -1,9 +1,9 @@
 {
     "git": {
-        "git_revision": "7c74f6a655c44af47be9e328e65c47a9740ac19c", 
+        "git_revision": "37bcf558d16088130edafc41561d5c7f8910686a", 
         "remote": "https://git.mozilla.org/releases/gaia.git", 
         "branch": ""
     }, 
-    "revision": "5ee161a90d087f4f72a6b35dd3b4a5f0662acf1b", 
+    "revision": "12e4908f7b76589a05762790a6c809fd9381f4fd", 
     "repo_path": "integration/gaia-central"
 }