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

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https://hg.mozilla.org/integration/gaia-central/rev/23b8db99bea6
Author: Jim Porter <squibblyflabbetydoo@gmail.com>
Desc: Merge pull request #13717 from jimporter/music-iac-restart

Bug 934011 - [music] Force closing the Music app breaks the controls; r=alive

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https://hg.mozilla.org/integration/gaia-central/rev/a9152815f9fd
Author: Jim Porter <jporter@mozilla.com>
Desc: Bug 934011 - [music] Force closing the Music app breaks the controls

b2g/config/gaia.json

 {
-    "revision": "7d0200d2ebc43c510e43a6486889f80a1fc9cfa5", 
+    "revision": "23b8db99bea6d36b3c8b36d3f2e489cf50fdbbfb", 
     "repo_path": "/integration/gaia-central"
 }