Bumping gaia.json for 3 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/5662c54c7f6e
Author: Hubert Figuière <hub@figuiere.net>
Desc: Merge pull request #31589 from hfiguiere/bug1196438-activity-test

Bug 1220776 and Bug 1196438

Fixing overlay display (DB race condition), fix tests for overlay and reenable activity test.

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https://hg.mozilla.org/integration/gaia-central/rev/19abb443a585
Author: Hubert Figuière <hub@figuiere.net>
Desc: Bug 1196438 - Reenable activity test.

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https://hg.mozilla.org/integration/gaia-central/rev/dc45c210c618
Author: Justin D'Arcangelo <justindarc@gmail.com>
Desc: Bug 1200776 - [Music][NGA] Overlays never appear on b2g-desktop

b2g/config/gaia.json

@@ -1,9 +1,9 @@
 {
     "git": {
-        "git_revision": "b75979ec8862bd5799a7c42e938d3f67be38d6ae", 
+        "git_revision": "8c8f9093753f2101c9de9b51f04fead8d2e177c7", 
         "remote": "https://git.mozilla.org/releases/gaia.git", 
         "branch": ""
     }, 
-    "revision": "f919c5b5f0f0b6fd3ef3346850710edafa2a615b", 
+    "revision": "5662c54c7f6ef01d8e12fb4332333715fcec3752", 
     "repo_path": "integration/gaia-central"
 }