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

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https://hg.mozilla.org/integration/gaia-central/rev/d84ca6d2cb4d
Author: Evyatar Amitay <evyatron@gmail.com>
Desc: Merge pull request #12617 from EverythingMe/923095-entertainment-bgimage

[Bug 923095] fix entertainment bgimage [r=ranbena]

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https://hg.mozilla.org/integration/gaia-central/rev/5d3cbdba7d88
Author: Evyatar Amitay <evyatron@gmail.com>
Desc: [Bug 923095] fix entertainment bgimage [r=ranbena]

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https://hg.mozilla.org/integration/gaia-central/rev/a326226a1cf4
Author: Evyatar Amitay <evyatron@gmail.com>
Desc: Merge pull request #12583 from EverythingMe/bugfix-loading-align

[Bug 922192] Fix loading indicator position [r=ranbena]

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https://hg.mozilla.org/integration/gaia-central/rev/9efd59e29cfd
Author: Evyatar Amitay <evyatron@gmail.com>
Desc: [Bug 922192] Fix loading indicator position [r=ranbena]