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

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https://hg.mozilla.org/integration/gaia-central/rev/4c7b6effecf4
Author: David Flanagan <dflanagan@mozilla.com>
Desc: Merge pull request #20175 from davidflanagan/bug995540-master

Merge pull request #19409 from dmarcos/bug995540 r=dmarcos

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https://hg.mozilla.org/integration/gaia-central/rev/4787cfb14cd1
Author: Diego Marcos <diego.marcos@gmail.com>
Desc: Merge pull request #19409 from dmarcos/bug995540

Bug 995540 - [Sora][camera]video recording would not stop instantly when...(cherry picked from commit 93623f6435849cc9f54d9996e8e64828ac9091d1)

Conflicts:

	apps/camera/js/app.js
	apps/camera/js/controllers/camera.js
	apps/system/js/attention_screen.js

b2g/config/gaia.json

@@ -4,6 +4,6 @@
         "remote": "", 
         "branch": ""
     }, 
-    "revision": "8ff2792c4485193da7e111fb91a1f4ca27ac508f", 
+    "revision": "4c7b6effecf47bb19ed9f001a4cbe909c17e9456", 
     "repo_path": "/integration/gaia-central"
 }