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

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https://hg.mozilla.org/integration/gaia-central/rev/9abc08d753dd
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Merge pull request #20120 from etiennesegonzac/bug-1021533

Bug 1021533 - (bug 1018836 follow up) css class cleanup. r=alive

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https://hg.mozilla.org/integration/gaia-central/rev/ff83f8ebf58f
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Bug 1021533 - (bug 1018836 follow up) css class cleanup.

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https://hg.mozilla.org/integration/gaia-central/rev/97311ba85093
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Merge pull request #20116 from etiennesegonzac/bug-1021237

Bug 1021237 - Make the edge zones higher in landscape mode. r=21

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https://hg.mozilla.org/integration/gaia-central/rev/d99a8e7375d1
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Bug 1021237 - Make the edge zones higher in landscape mode.
Bumping manifests a=b2g-bump