Bumping gaia.json for 3 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/643dbb1c26d3
Author: Chris Lord <chrislord.net@gmail.com>
Desc: Merge pull request #26006 from Cwiiis/bug1082675-app-grouping-by-default

Bug 1082675 - Enable homescreen app-grouping permanently. r=kgrandon,crdlc

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https://hg.mozilla.org/integration/gaia-central/rev/01889de35710
Author: Chris Lord <chrislord.net@gmail.com>
Desc: Bug 1082675 - Fix divider->group related marionette test failures. r=crdlc,kgrandon

Some assumptions made by marionette tests no longer hold after enabling
app-grouping by default:

- Long-pressing a divider no longer brings up the context menu
- The divider element itself is not positioned (its children are)

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https://hg.mozilla.org/integration/gaia-central/rev/89e940eb62b0
Author: Chris Lord <chrislord.net@gmail.com>
Desc: Bug 1082675 - Enable homescreen app-grouping permanently. r=kgrandon,crdlc

This reverts commit 071efd0eb9d962d4f96edc28d672e48910f48387.
Bumping manifests a=b2g-bump