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

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https://hg.mozilla.org/integration/gaia-central/rev/cd54d6fb66f4
Author: James Lal <james@lightsofapollo.com>
Desc: Merge pull request #12403 from lightsofapollo/revert-905116

Revert "Merge pull request #12086 from alivedise/bugzilla/905116_master_...

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https://hg.mozilla.org/integration/gaia-central/rev/ad8da2ba7daa
Author: James Lal <james@lightsofapollo.com>
Desc: Revert "Merge pull request #12086 from alivedise/bugzilla/905116_master_v4_test/homescreen-launcher"

This reverts commit 3408cc3f6b190c8cd31832fbb8cd2ae571041f29, reversing
changes made to 41d0776a8745e93f4437111d1a09f483127db22c.

b2g/config/gaia.json

@@ -1,4 +1,4 @@
 {
-    "revision": "858a8bc1d64f9360d8c8df0e531b059788d9b543", 
+    "revision": "cd54d6fb66f4abe609c742a91d15d15d738befb4", 
     "repo_path": "/integration/gaia-central"
 }