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

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https://hg.mozilla.org/integration/gaia-1_4/rev/ca559cb3cdba
Author: Arthur Chen <crh0716@gmail.com>
Desc: Merge pull request #18833 from crh0716/993161_v1.4

Bug 993161 - Ensure the value of 'ril.iccInfo.mbdn' is valid when starting up r=jaoo

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https://hg.mozilla.org/integration/gaia-1_4/rev/73607c562e3d
Author: Arthur Chen <crh0716@gmail.com>
Desc: Bug 993161 - Ensure the value of 'ril.iccInfo.mbdn' is valid when starting up
Bumping manifests a=b2g-bump