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

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https://hg.mozilla.org/integration/gaia-central/rev/6b3922b505b1
Author: Borja Salguero <borjasalguero@users.noreply.github.com>
Desc: Merge pull request #11897 from gasolin/issue-911684

Bug 911684 - [FTU] hide SIM contact import when not support telephony r=borjasalguero

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https://hg.mozilla.org/integration/gaia-central/rev/4a6100bd2ea8
Author: gasolin <gasolin@gmail.com>
Desc: Bug 911684 - [FTU] hide SIM contact import when not support telephony

b2g/config/gaia.json

@@ -1,4 +1,4 @@
 {
-    "revision": "6f431b85934673ef7fff3ae48665b245d47293df", 
+    "revision": "6b3922b505b1686e2a59226ee2977b022bee3406", 
     "repo_path": "/integration/gaia-central"
 }