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

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https://hg.mozilla.org/integration/gaia-central/rev/f90959f4b45c
Author: Zac <zcampbell@mozilla.com>
Desc: Merge pull request #16376 from zacc/bug_973593

Bug 973593 - Address failure in test_cost_control_data_alert_mobile.py

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https://hg.mozilla.org/integration/gaia-central/rev/e19ec800f31e
Author: Zac Campbell <zcampbell@mozilla.com>
Desc: Bug 973593 - Address failure in test_cost_control_data_alert_mobile.py
Bumping manifests a=b2g-bump