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

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https://hg.mozilla.org/integration/gaia-central/rev/c58a78c93c48
Author: gasolin <gasolin@gmail.com>
Desc: Merge pull request #12914 from gasolin/issue-927749-2

Bug 927749 - [Flatfish][Homescreen] hide add collection menu option when..., r=crdlc

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https://hg.mozilla.org/integration/gaia-central/rev/a54120656789
Author: gasolin <gasolin@gmail.com>
Desc: Bug 927749 - [Flatfish][Homescreen] hide add collection menu option when searchbar is hidden

b2g/config/gaia.json

@@ -1,4 +1,4 @@
 {
-    "revision": "4b22cf21e5ff7d46d743bcdb6b9d6ea2a3f1ba82", 
+    "revision": "c58a78c93c48bf87c72d77497e63f13680be9cb8", 
     "repo_path": "/integration/gaia-central"
 }