Bumping gaia.json for 4 gaia-central revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/28944ec8ca72
Author: Anthony Ricaud <anthony@ricaud.me>
Desc: Bug 949897 - Disable test_cards_view_kill_apps_with_two_apps.py r=me

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https://hg.mozilla.org/integration/gaia-central/rev/2b84917bc9f1
Author: Jose Antonio Olivera Ortega <josea.olivera@gmail.com>
Desc: Merge pull request #14604 from jaoo/928294

Bug 928294 - [DSDS][Gaia] Settings app should support call settings of multiple sim cards. r=arthurcc

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https://hg.mozilla.org/integration/gaia-central/rev/2e916b992987
Author: Jose Antonio Olivera Ortega <josea.olivera@gmail.com>
Desc: Bug 928294 - [DSDS][Gaia] Settings app should support call settings of multiple sim cards

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https://hg.mozilla.org/integration/gaia-central/rev/dace64b0307f
Author: Bebe <bebe@mozilla.ro>
Desc: Bug 949405 - Bump gaiatest version to 0.21.2. r=dhunt