Bumping gaia.json for 4 gaia-central revision(s)

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https://hg.mozilla.org/integration/gaia-central/rev/c2a13d1a2278
Author: John Hu <johu@mozilla.com>
Desc: Merge pull request #11210 from huchengtw-moz/video/Bug_898324_there_is_1px_shifting

Bug 898324 - There is 1px shifting down of selection border, r=rexboy

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https://hg.mozilla.org/integration/gaia-central/rev/ebdadf56095e
Author: John Hu <johu@mozilla.com>
Desc: Bug 898324 - There is 1px shifting down of selection border

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https://hg.mozilla.org/integration/gaia-central/rev/473773a65d55
Author: John Hu <johu@mozilla.com>
Desc: Merge pull request #11207 from huchengtw-moz/video/Bug_898377_missing_1.5x_icon

Bug 898377 - The 1.5x icon is missing in Video app on Gaia master branch, r=rexboy

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https://hg.mozilla.org/integration/gaia-central/rev/e32d1a3520c0
Author: John Hu <johu@mozilla.com>
Desc: Bug 898377 - The 1.5x icon is missing in Video app on Gaia master branch

b2g/config/gaia.json

@@ -1,4 +1,4 @@
 {
-    "revision": "a36df4782c679df0ccb69a3472fb0b414f5ff7a7", 
+    "revision": "c2a13d1a22786ba0c9d1be6a9791e2db09ba4983", 
     "repo_path": "/integration/gaia-central"
 }