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

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https://hg.mozilla.org/integration/gaia-central/rev/991ab3659c6e
Author: Jose Antonio Olivera Ortega <josea.olivera@gmail.com>
Desc: Merge pull request #15156 from jaoo/956945

Bug 956945 - [B2G][Settings] Voicemail number does not update after deleting the number. r=kaze

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https://hg.mozilla.org/integration/gaia-central/rev/0035a8df4b1c
Author: Jose Antonio Olivera Ortega <josea.olivera@gmail.com>
Desc: Bug 956945 - [B2G][Settings] Voicemail number does not update after deleting the number
Bumping manifests a=b2g-bump