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

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https://hg.mozilla.org/integration/gaia-central/rev/8983baf77549
Author: Timothy Guan-tin Chien <timdream@gmail.com>
Desc: Merge pull request #15035 from timdream/keyboard-remove-ime

Bug 956659 - Only include IMEs for selected layouts in the build, r=yurenju, djf

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https://hg.mozilla.org/integration/gaia-central/rev/842020b707e1
Author: Timothy Guan-tin Chien <timdream@gmail.com>
Desc: Bug 956659 - Only include IMEs for selected layouts in the build

b2g/config/gaia.json

@@ -1,4 +1,4 @@
 {
-    "revision": "8e10ff5b058125cd65ae0498e1ee2ab362d8ab72", 
+    "revision": "8983baf77549a33a1df7dbe71dcdab3eaf0f7b94", 
     "repo_path": "/integration/gaia-central"
 }