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

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https://hg.mozilla.org/integration/gaia-central/rev/9f9909a9fac7
Author: Yuren Ju <yurenju@gmail.com>
Desc: Merge pull request #16473 from yurenju/twice

Bug 974376 - Marionnette JS tests are reported twice on Travis and locally. r=@evanxd

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https://hg.mozilla.org/integration/gaia-central/rev/9728b78e745f
Author: Yuren Ju <yurenju@gmail.com>
Desc: Bug 974376 - Marionnette JS tests are reported twice on Travis and locally.

b2g/config/gaia.json

@@ -1,4 +1,4 @@
 {
-    "revision": "f90959f4b45cface91f0e52275e5ba61f73fc609", 
+    "revision": "9f9909a9fac7cbf1a3a2c3ad3e3f7e80426c357c", 
     "repo_path": "/integration/gaia-central"
 }