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

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https://hg.mozilla.org/integration/gaia-central/rev/973c592c3239
Author: chmanchester <chmanchester@users.noreply.github.com>
Desc: Merge pull request #22846 from chmanchester/gu-structured

Bug 1034274 - Use a structured logging reporter for Gaia Unit Tests;r=jgriffin

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https://hg.mozilla.org/integration/gaia-central/rev/a4ce23a9b13c
Author: chmanchester <cmanchester@mozilla.com>
Desc: Bug 1034274 - Use a structured logging reporter for Gaia Unit Tests;r=jgriffin

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https://hg.mozilla.org/integration/gaia-central/rev/85d8d91de7ee
Author: Wilson Page <wilsonpage@me.com>
Desc: Merge pull request #22919 from wilsonpage/1054005

Update gaia-icons#0.5.0 and gaia-header#v0.3.6

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https://hg.mozilla.org/integration/gaia-central/rev/a82ebccd26f3
Author: Wilson Page <wilsonpage@me.com>
Desc: Update shared gaia-icons#0.5.2 and gaia-header#v0.3.8
Bumping manifests a=b2g-bump