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

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https://hg.mozilla.org/integration/gaia-central/rev/9ce1816a59a5
Author: Borja Salguero <borjasalguero@users.noreply.github.com>
Desc: Merge pull request #15263 from borjasalguero/subject_banner

Bug 952109 - [message] Subject. The banner informing the user that the m...

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https://hg.mozilla.org/integration/gaia-central/rev/05758b707d86
Author: borjasalguero <fbsc@tid.es>
Desc: Bug 952109 - [message] Subject. The banner informing the user that the maximum length of subject has been reached obscures the subject text field r=schung
Bumping manifests a=b2g-bump