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

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https://hg.mozilla.org/integration/gaia-central/rev/e21670ef83d8
Author: Min-Zhong "John" Lu <mnjul@users.noreply.github.com>
Desc: Merge pull request #21492 from mnjul/bug_1033585_lockscreen_conns_sim_string_hardcoded

Bug 1033585 - [B2G][System][Lockscreen]: SIM 1 or SIM 2 not translated for Tamil. r=arthurcc

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https://hg.mozilla.org/integration/gaia-central/rev/848985243015
Author: John Lu [:mnjul] <jlu@mozilla.com>
Desc: Bug 1033585 - [B2G][System][Lockscreen]: SIM 1 or SIM 2 not translated for Tamil

b2g/config/gaia.json

@@ -4,6 +4,6 @@
         "remote": "", 
         "branch": ""
     }, 
-    "revision": "4177ded40ba284bcf42c8c71f2beb2700c9cc8d2", 
+    "revision": "e21670ef83d8c9701d22267561ad4db611893811", 
     "repo_path": "/integration/gaia-central"
 }