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

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https://hg.mozilla.org/integration/gaia-central/rev/b91bf20deb93
Author: Jose M. Cantera <jmcanterafonseca@gmail.com>
Desc: Merge pull request #15719 from rnowm/950803

Bug 950803 - [B2G][Contacts]When tapping on the Search box after a successful ...

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https://hg.mozilla.org/integration/gaia-central/rev/b90efa2c70e6
Author: rnowm <arnau@arnaumarch.com>
Desc: Bug 950803 - [B2G][Contacts]When tapping on the Search box after a successful Gmail contacts import, the on-device display is inappropriate
Bumping manifests a=b2g-bump