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

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https://hg.mozilla.org/integration/gaia-central/rev/76d64e56656e
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Merge pull request #23099 from KevinGrandon/bug_1056156_fix_system_app_install

Bug 1056156 - [System] Update AppInstall uninstall method

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https://hg.mozilla.org/integration/gaia-central/rev/1c002c0d049d
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 1056156 - [System] Update AppInstall uninstall method r=fabrice

b2g/config/gaia.json

@@ -4,6 +4,6 @@
         "remote": "", 
         "branch": ""
     }, 
-    "revision": "ecfb8305745716f534e782c7b9df11aaa78b3823", 
+    "revision": "76d64e56656e4f04e2bfc8e6e7a93a42f411e452", 
     "repo_path": "/integration/gaia-central"
 }