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

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https://hg.mozilla.org/integration/gaia-central/rev/39938f581efd
Author: John Hu <johu@mozilla.com>
Desc: Merge pull request #12012 from huchengtw-moz/video/Bug_910094_ui_polish

Bug 910094 - [Video] - UI Fixes in Gallery View and Video Player, r=djf

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https://hg.mozilla.org/integration/gaia-central/rev/eece41240fe6
Author: John Hu <johu@mozilla.com>
Desc: Bug 910094 - [Video] - UI Fixes in Gallery View and Video Player

b2g/config/gaia.json

@@ -1,4 +1,4 @@
 {
-    "revision": "c96e0e230e9dba0fcc7f7a6bfb76d85a62fb95c5", 
+    "revision": "39938f581efd6d7a4a6ccaf1cf8d77b8d93e1c2b", 
     "repo_path": "/integration/gaia-central"
 }