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

========

https://hg.mozilla.org/integration/gaia-central/rev/91805a7dc452
Author: autolander <bug.autolander@gmail.com>
Desc: Bug 1165257 - merge pull request #30081 from KevinGrandon:bug_1165257_ringtones_template_strings to mozilla-b2g:master

========

https://hg.mozilla.org/integration/gaia-central/rev/90c394c1ffe0
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 1165257 - [Ringtones] Migrate to tagged template strings r=squib

b2g/config/gaia.json

@@ -1,9 +1,9 @@
 {
     "git": {
-        "git_revision": "a3312da974f3773f0ceb57c0af9b2a459971668f", 
+        "git_revision": "91a9887f2768b4ebd9a30f8651a387a7ea41c96b", 
         "remote": "https://git.mozilla.org/releases/gaia.git", 
         "branch": ""
     }, 
-    "revision": "f0e03729e38b5ddae5951ec891b33a04905c780a", 
+    "revision": "91805a7dc452d2379bbded87b684aafa4d4f7b3a", 
     "repo_path": "integration/gaia-central"
 }