Bumping gaia.json for 1 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/765bd1e5dbef
Author: Ed Morley <emorley@mozilla.com>
Desc: Revert "Bug 975161 - Ensure SIM Pin inputs are visible. r=vingetun" for failures in system/test/unit/sim_settings_helper_test.js

This reverts commit fa25ec9e9491388beee916b35ad3c59cbfee2f30.
Bumping manifests a=b2g-bump