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

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https://hg.mozilla.org/integration/gaia-central/rev/1b8b899e99f7
Author: Yura Zenevich <yura.zenevich@gmail.com>
Desc: Merge pull request #22593 from yzen/bug-1030431

Bug 1030431 - correctly handling dialog overlay visibility in the dialer...

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https://hg.mozilla.org/integration/gaia-central/rev/b911cda448ae
Author: Yura Zenevich <yzenevich@mozilla.com>
Desc: Bug 1030431 - correctly handling dialog overlay visibility in the dialer and callscreen apps.

b2g/config/gaia.json

@@ -4,6 +4,6 @@
         "remote": "", 
         "branch": ""
     }, 
-    "revision": "eb0333099b931335af738d24ef1a48f01de0be1a", 
+    "revision": "1b8b899e99f7f8605454985c7bc2c9a12935e70c", 
     "repo_path": "/integration/gaia-central"
 }