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

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https://hg.mozilla.org/integration/gaia-central/rev/e21670ef83d8
Author: Min-Zhong "John" Lu <mnjul@users.noreply.github.com>
Desc: Merge pull request #21492 from mnjul/bug_1033585_lockscreen_conns_sim_string_hardcoded

Bug 1033585 - [B2G][System][Lockscreen]: SIM 1 or SIM 2 not translated for Tamil. r=arthurcc

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https://hg.mozilla.org/integration/gaia-central/rev/848985243015
Author: John Lu [:mnjul] <jlu@mozilla.com>
Desc: Bug 1033585 - [B2G][System][Lockscreen]: SIM 1 or SIM 2 not translated for Tamil
Bumping manifests a=b2g-bump