Bumping gaia.json for 6 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/17205e343e7e
Author: Gregor Wagner <anygregor@gmail.com>
Desc: Merge pull request #18601 from gregorwagner/999572

Bug 999572 - Fix settingsService usage in NetworkGeolocationProvider.js

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https://hg.mozilla.org/integration/gaia-central/rev/8ad0e3106fe3
Author: Gregor Wagner <anygregor@gmail.com>
Desc: Bug 999572 - Fix settingsService usage in NetworkGeolocationProvider.js

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https://hg.mozilla.org/integration/gaia-central/rev/d1c1d17679d5
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Merge pull request #18543 from KevinGrandon/bug_999676_app_manager_homescreen_visibility

Bug 999676 - [System] Remove un-needed homescreen visibility setting r=alive

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https://hg.mozilla.org/integration/gaia-central/rev/3fd8382d7c5f
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 999676 - [System] Remove un-needed homescreen visibility setting r=alive

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https://hg.mozilla.org/integration/gaia-central/rev/be29770fd678
Author: Diego Marcos <diego.marcos@gmail.com>
Desc: Merge pull request #18594 from dmarcos/bug998478

Bug 998478 - [Camera] [Madai] The setting menu button when open doesn't ...

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https://hg.mozilla.org/integration/gaia-central/rev/e4253836a5c8
Author: Wilson Page <wilsonpage@me.com>
Desc: Bug 998478 - [Camera] [Madai] The setting menu button when open doesn't overlap with the hud button
Bumping manifests a=b2g-bump