Bumping gaia.json for 3 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/2f15fe97023b
Author: Jose M. Cantera <jmcanterafonseca@gmail.com>
Desc: Merge pull request #18971 from jmcanterafonseca/fix_call_log

Bug 1003979 - [B2G][Open_C][Dialer]Contact picture does not appear in th...

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https://hg.mozilla.org/integration/gaia-central/rev/a28733377f9e
Author: Jose M. Cantera <jmcanterafonseca@gmail.com>
Desc: Bug 1003979 - [B2G][Open_C][Dialer]Contact picture does not appear in the call log

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https://hg.mozilla.org/integration/gaia-central/rev/7d58ab692c64
Author: Dale Harvey <dale@arandomurl.com>
Desc: Bug 1010537 - Move css overrides from locales file to CSS. r=benfrancis
Bumping manifests a=b2g-bump