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

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https://hg.mozilla.org/integration/gaia-1_3/rev/6aa6048ae77e
Author: Ryan VanderMeulen <rvandermeulen@mozilla.com>
Desc: Merge pull request #19891 from malini/v1.3

Bug 994176  -need to use marionette_client_mozilla_b2g28_v1_3 instead of tip marionet...

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https://hg.mozilla.org/integration/gaia-1_3/rev/793ee5159558
Author: Malini Das <mdas@mozilla.com>
Desc: need to use marionette_client_mozilla_b2g28_v1_3 instead of tip marionette_client
Bumping manifests a=b2g-bump