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

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https://hg.mozilla.org/integration/gaia-central/rev/26f2c60c0ba0
Author: Timothy Guan-tin Chien <timdream@gmail.com>
Desc: Merge pull request #18440 from leob2g/bug988660

Bug 988660 - Notification remove array item issue in notification_helper, r=etienne

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https://hg.mozilla.org/integration/gaia-central/rev/6c1266b0ff25
Author: youngsu.rho <youngsu.rho@lge.com>
Desc: Bug 988660 - Notification remove array item issue in notification_helper
Bumping manifests a=b2g-bump