Bumping gaia.json for 4 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/8caf1b8e97f9
Author: Michael Henretty <michael.henretty@gmail.com>
Desc: Merge pull request #28904 from mikehenrty/bug-1142925-notification-auto-dir

Bug 1142925 - Use dir=auto for notification title text, but ensure it te...

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https://hg.mozilla.org/integration/gaia-central/rev/686cedba8248
Author: Michael Henretty <michael.henretty@gmail.com>
Desc: Bug 1142925 - Use dir=auto for notification title text, but ensure it text-aligns right

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https://hg.mozilla.org/integration/gaia-central/rev/db91a6d8bbb6
Author: autolander <bug.autolander@gmail.com>
Desc: Bug 1143716 - merge pull request #28917 from mwargers:test_delete_call_log to mozilla-b2g:master

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https://hg.mozilla.org/integration/gaia-central/rev/86f4353585fc
Author: Martijn Wargers <mwargers@mozilla.com>
Desc: Bug 1143716 - test_delete_call_log::test_delete_call_log() failed with AssertionError

b2g/config/gaia.json

@@ -1,9 +1,9 @@
 {
     "git": {
-        "git_revision": "b4066c9668fbc69af468c4f625d7bf0ee8607280", 
+        "git_revision": "73d838c74b771361bd36dce9c4e2d2ecf2a0dd2e", 
         "remote": "https://git.mozilla.org/releases/gaia.git", 
         "branch": ""
     }, 
-    "revision": "41ad5f0f8bbb88fcda56e8e831df2070c7e83516", 
+    "revision": "8caf1b8e97f9ee342f4aba02e7d16f4442ba7caf", 
     "repo_path": "integration/gaia-central"
 }