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

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https://hg.mozilla.org/integration/gaia-central/rev/477e7a5c5977
Author: Cristian Rodriguez <crdlc@tid.es>
Desc: Merge pull request #12367 from crdlc/bug-919458

Bug 919458 - Banner display none in order not to consume memory

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https://hg.mozilla.org/integration/gaia-central/rev/d67e4dd49247
Author: crdlc <crdlc@tid.es>
Desc: Bug 919458 - Banner display none in order not to consume memory

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https://hg.mozilla.org/integration/gaia-central/rev/0a66c69f06c5
Author: Cristian Rodriguez <crdlc@tid.es>
Desc: Merge pull request #12389 from crdlc/bug-919933

Bug 919933 - [Homescreen] Lazy load shared/js/omadrm/fl.js

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https://hg.mozilla.org/integration/gaia-central/rev/ad2a3ac5e3e1
Author: crdlc <crdlc@tid.es>
Desc: Bug 919933 - [Homescreen] Lazy load shared/js/omadrm/fl.js