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

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https://hg.mozilla.org/integration/gaia-2_0/rev/6b5977ff4085
Author: Anthony Ricaud <anthony@ricaud.me>
Desc: Merge pull request #20303 from Rik/keyboard-hide-toolbar-1019426

Bug 1019426 - When searching in the Address Book from the Dialer a white... r=etienne

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https://hg.mozilla.org/integration/gaia-2_0/rev/4064d0de4e16
Author: Jared Hirsch <ohai@6a68.net>
Desc: Merge pull request #19792 from 6a68/bug-1011498-scale-fxa-bkgd-imgs

Bug 1011498 - Force FxA background images to scale to different resolution screens

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https://hg.mozilla.org/integration/gaia-2_0/rev/dbf0b157d833
Author: Julien Wajsberg <felash@gmail.com>
Desc: Merge pull request #20578 from julienw/1022096-ellipsis-in-delete-mode

Bug 1022096 - [Messages] sms text truncated in delete messages mode r=az...

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https://hg.mozilla.org/integration/gaia-2_0/rev/5c5f4dade963
Author: Julien Wajsberg <felash@gmail.com>
Desc: Merge pull request #20455 from julienw/1018035-cursor-hidden-activity

Bug 1018035 - [Flame][v1.4][SMS]No cursor display when tap the message e...
Bumping manifests a=b2g-bump