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

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https://hg.mozilla.org/integration/gaia-central/rev/d028d7aa4438
Author: John Hu <johu@mozilla.com>
Desc: Merge pull request #13738 from huchengtw-moz/camera/Bug_939047_black_border_on_left_side

Bug 939047 - [B2G][Helix][camera][dingyu]The camera preview is not corre..., r=djf

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https://hg.mozilla.org/integration/gaia-central/rev/6b42e8db6a97
Author: John Hu <johu@mozilla.com>
Desc: Bug 939047 - [B2G][Helix][camera][dingyu]The camera preview is not correct and the left of the screen have a black area in hd device

b2g/config/gaia.json

 {
-    "revision": "7385c208e70665070d529a195fe2043d47e7b0c1", 
+    "revision": "d028d7aa4438f87a196471d4e6429b29b62de414", 
     "repo_path": "/integration/gaia-central"
 }