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

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https://hg.mozilla.org/integration/gaia-central/rev/f4d91b78c737
Author: George <georgeiscoming@gmail.com>
Desc: Merge pull request #16026 from cctuan/968667

Bug 968667 - Add run-app-js-command

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https://hg.mozilla.org/integration/gaia-central/rev/8f01711ff0e4
Author: cctuan <georgeiscoming@gmail.com>
Desc: Bug 968667 - Add run-app-js-command
Bumping manifests a=b2g-bump