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

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https://hg.mozilla.org/integration/gaia-central/rev/5208f7d41f2f
Author: Jose M. Cantera <jmcanterafonseca@gmail.com>
Desc: Merge pull request #13531 from fcampo/retry-import-Contacts-935301

Bug 935301 - [Contacts] Clicking retry on error while importing from SD doesn't retry

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https://hg.mozilla.org/integration/gaia-central/rev/4f4b4afb3d50
Author: Fernando Campo <fernando.campo@o2.com>
Desc: Bug 935301 - [Contacts] Clicking retry on error while importing from SD doesn't retry