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

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https://hg.mozilla.org/integration/gaia-central/rev/259568db63e1
Author: John Hu <johu@mozilla.com>
Desc: Merge pull request #19024 from huchengtw-moz/Stingray/Bug_1006378-selection-border

Bug 1006378 - [Stingray] Add selection border support to homescreen-stin..., r=garychen, r=lchang

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https://hg.mozilla.org/integration/gaia-central/rev/6833725517e6
Author: John Hu <johu@mozilla.com>
Desc: Bug 1006378 - [Stingray] Add selection border support to homescreen-stingray

b2g/config/gaia.json

@@ -4,6 +4,6 @@
         "remote": "", 
         "branch": ""
     }, 
-    "revision": "d13cf5aace9f5e02caf18b73d42dcecb76b5a63d", 
+    "revision": "259568db63e155b5c40102aef955b79c8097aade", 
     "repo_path": "/integration/gaia-central"
 }