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

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https://hg.mozilla.org/integration/gaia-central/rev/480f4b58108b
Author: Fernando Campo <fcampo@users.noreply.github.com>
Desc: Merge pull request #21875 from empoalp/bug-995938

Bug 995938 - Device does not play an 'end tone' when the call is finished (r=etienne)

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https://hg.mozilla.org/integration/gaia-central/rev/35f7a7e5d36b
Author: David Garcia <davidg@tid.es>
Desc: Bug 995938 - Device does not play an 'end tone' when the call is finished
Bumping manifests a=b2g-bump