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

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https://hg.mozilla.org/integration/gaia-1_4/rev/df7f782aae58
Author: Ryan VanderMeulen <rvandermeulen@mozilla.com>
Desc: Merge pull request #21366 from jimporter/ringtones-mp3-1.4

Bug 1032702 - [v1.4] Cannot select preloaded MP3 as ringtone

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https://hg.mozilla.org/integration/gaia-1_4/rev/90c0f5ed91f1
Author: Jim Porter <jporter@mozilla.com>
Desc: Bug 1032702 - [v1.4] Cannot select preloaded MP3 as ringtone
Bumping manifests a=b2g-bump