Bumping gaia.json for 2 gaia-central revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/f0d719eccb3f
Author: Jim Porter <squibblyflabbetydoo@gmail.com>
Desc: Merge pull request #12596 from jimporter/music-lockscreen-2

Bug 891024 - [Music] [User Story] Provide access to music player controls when the screen is locked

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https://hg.mozilla.org/integration/gaia-central/rev/a4f7723a76de
Author: Jim Porter <jporter@mozilla.com>
Desc: Bug 891024 - [music] Add media playback controls to the lockscreen; r=alive, ui-r=jsavory, f=gaye, f=eragonj