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

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https://hg.mozilla.org/integration/gaia-central/rev/ffb71c2169b8
Author: Francisco Jordano <arcturus@ardeenelinfierno.com>
Desc: Merge pull request #17760 from arcturus/bug-984800-2

Bug 984800 - [MADAI][Contacts] @2.25x assets update for Contacts

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https://hg.mozilla.org/integration/gaia-central/rev/ec27e1b0c952
Author: Francisco Jordano <arcturus@ardeenelinfierno.com>
Desc: Bug 984800 - [MADAI][Contacts] @2.25x assets update for Contacts

Now images optimized
Bumping manifests a=b2g-bump