Bumping gaia.json for 1 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-1_4/rev/a0503a2e8fdc
Author: Jim Porter <jporter@mozilla.com>
Desc: Merge pull request #20397 from jimporter/email-as-user-agent

Bug 880670 - [email/activesync] some ActiveSync implementations blacklis...
Bumping manifests a=b2g-bump