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

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https://hg.mozilla.org/integration/gaia-central/rev/71c67d15646d
Author: Chris Lord <chrislord.net@gmail.com>
Desc: Merge pull request #25499 from Cwiiis/bug1086523-compact-group-headers

Bug 1086523 - Compact group headers. r=crdlc

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https://hg.mozilla.org/integration/gaia-central/rev/ef0fd4fe46f6
Author: Chris Lord <chrislord.net@gmail.com>
Desc: Bug 1086523 - Make collapsed groups more compact. r=crdlc

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https://hg.mozilla.org/integration/gaia-central/rev/b3a776c7b671
Author: Chris Lord <chrislord.net@gmail.com>
Desc: Bug 1086523 - Make group header more compact. r=crdlc

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https://hg.mozilla.org/integration/gaia-central/rev/417a49a3ce12
Author: Chris Lord <chrislord.net@gmail.com>
Desc: Bug 1086523 - Remove group naming. r=crdlc
Bumping manifests a=b2g-bump