Bumping gaia.json for 3 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/75d8e419442b
Author: Germán Toro del Valle <gtorodelvalle@gmail.com>
Desc: Merge pull request #22075 from empoalp/bug_976678

Bug 976678 - [zffos1.3][P3](Local) During voice calls the sound alert fo...

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https://hg.mozilla.org/integration/gaia-central/rev/bfeab1ed2347
Author: David Garcia <davidg@tid.es>
Desc: fixup

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https://hg.mozilla.org/integration/gaia-central/rev/e58cadff8d2c
Author: David Garcia <davidg@tid.es>
Desc: Bug 976678 - [zffos1.3][P3](Local) During voice calls the sound alert for new SMS does not beep.
Bumping manifests a=b2g-bump