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

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https://hg.mozilla.org/integration/gaia-central/rev/2abf97674c6a
Author: James Lal <james@lightsofapollo.com>
Desc: Merge pull request #12279 from lightsofapollo/disable-modify-event-view

disable modify_event_test a=test-only

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https://hg.mozilla.org/integration/gaia-central/rev/b12465654e88
Author: James Lal <james@lightsofapollo.com>
Desc: disable modify_event_test a=test-only

b2g/config/gaia.json

@@ -1,4 +1,4 @@
 {
-    "revision": "49950f830ee6c3543501b959fe2d3b88912b7278", 
+    "revision": "2abf97674c6a9801e8dbf1d85bdd2c6178c90a19", 
     "repo_path": "/integration/gaia-central"
 }