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

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https://hg.mozilla.org/integration/gaia-central/rev/da052e190cb5
Author: Marcus Cavanaugh <m@mcav.com>
Desc: Merge pull request #15923 from mcav/timer-button-sizes

Bug 951092 - [Clock] Adjust Pause/Cancel buttons size and style in Timer...

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https://hg.mozilla.org/integration/gaia-central/rev/52a46c9246b9
Author: Marcus Cavanaugh <m@mcav.com>
Desc: Bug 951092 - [Clock] Adjust Pause/Cancel buttons size and style in Timer. r=jburke

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https://hg.mozilla.org/integration/gaia-central/rev/4c25b1959b1c
Author: Dominic Kuo <dkuo@mozilla.com>
Desc: Merge pull request #16039 from dominickuo/bug-946556-new

Bug 946556 - [Music] Disable the play controls when using a bluetooth headset in a call, r=jimporter

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https://hg.mozilla.org/integration/gaia-central/rev/86228d986b47
Author: Dominic Kuo <dkuo@mozilla.com>
Desc: Bug 946556 - [Music] Disable the play controls when using a bluetooth headset in a call
Bumping manifests a=b2g-bump