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

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https://hg.mozilla.org/integration/gaia-central/rev/5b157e823d42
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Merge pull request #16514 from etiennesegonzac/missing-git-ignore

Bug 975395 - Add missing gitignores for the directories created by running a make test-integration. r=kgrandon

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https://hg.mozilla.org/integration/gaia-central/rev/b0411430cccd
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Bug 975395 - Add missing gitignores for the directories created by running a make test-integration.

b2g/config/gaia.json

@@ -1,4 +1,4 @@
 {
-    "revision": "ea49a842004915e5448941effb88b61579ff5b2a", 
+    "revision": "5b157e823d42532a365d33cfe3a8bd9ba4b71152", 
     "repo_path": "/integration/gaia-central"
 }