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

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https://hg.mozilla.org/integration/gaia-central/rev/48d949a1929d
Author: Zac <zcampbell@mozilla.com>
Desc: Merge pull request #15981 from zacc/bug_968120

Bug 968120 - Address test_lockscreen_unlock_to_emergency_call intermitte...

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https://hg.mozilla.org/integration/gaia-central/rev/a35dc4fdef26
Author: Zac Campbell <zcampbell@mozilla.com>
Desc: Bug 968120 - Address test_lockscreen_unlock_to_emergency_call intermittent Travis/TBPL
Bumping manifests a=b2g-bump