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

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https://hg.mozilla.org/integration/gaia-central/rev/84fc66fbc276
Author: evanxd <itoyxd@gmail.com>
Desc: Merge pull request #11777 from evanxd/bug-863999

Bug 863999 - Header in week view displays two months without a separator

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https://hg.mozilla.org/integration/gaia-central/rev/b58c1c2b6395
Author: Evan Xd <itoyxd@gmail.com>
Desc: Bug 863999 - Should have a space between two months.

b2g/config/gaia.json

@@ -1,4 +1,4 @@
 {
-    "revision": "ca50a633ddfe26b08ac3ad9b19047f43e9680a4a", 
+    "revision": "84fc66fbc2761d234ef61237379e5f0966846bd5", 
     "repo_path": "/integration/gaia-central"
 }