Bumping gaia.json for 3 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/4fc562ca01a3
Author: Evan Tseng <itoyxd@gmail.com>
Desc: Merge pull request #31075 from alastor0325/bug-1185733

Bug 1185733 - change audio channel type to system r=gsvelto

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https://hg.mozilla.org/integration/gaia-central/rev/ae5afacdab91
Author: Alastor Wu <alwu@mozilla.com>
Desc: Bug 1185733 - change audio channel type to system

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https://hg.mozilla.org/integration/gaia-central/rev/43cf17dec2e7
Author: Alastor Wu <alwu@mozilla.com>
Desc: Bug 1185733 - change audio channel type to system

b2g/config/gaia.json

 {
     "git": {
-        "git_revision": "f0eebf83d57397bc5fd95ccbbe55b5ae3a0d5815", 
+        "git_revision": "a8319543833b08e986fa3ed590faeb2624bf1683", 
         "remote": "https://git.mozilla.org/releases/gaia.git", 
         "branch": ""
     }, 
-    "revision": "f66686ed7ca139dd407a1e8207965c9ebc5bf03c", 
+    "revision": "4fc562ca01a3e8e17dd042af9076f1fe7bc8f91d", 
     "repo_path": "integration/gaia-central"
 }