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

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https://hg.mozilla.org/integration/gaia-central/rev/a8f8d540eb85
Author: gasolin <gasolin@gmail.com>
Desc: Merge pull request #14681 from gasolin/issue-950082

Revert "Merge pull request #13875 from gasolin/issue-939011"

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https://hg.mozilla.org/integration/gaia-central/rev/ba8d8fc12ace
Author: gasolin <gasolin@gmail.com>
Desc: Revert "Merge pull request #13875 from gasolin/issue-939011"

This reverts commit 204d32ec1dfa27d87b8ee43ae17b65c005c52b45, reversing
changes made to 97fe3c8a60623821fd0ec265fb11786c3ab50431.

b2g/config/gaia.json

@@ -1,4 +1,4 @@
 {
-    "revision": "345f6904606712c9029d13a19bb59f93616aa18d", 
+    "revision": "a8f8d540eb85be0e7eeda4932cd68b9bea9fc71e", 
     "repo_path": "/integration/gaia-central"
 }