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

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https://hg.mozilla.org/integration/gaia-central/rev/8bdc10e2089f
Author: Zac <zcampbell@mozilla.com>
Desc: Merge pull request #15975 from zacc/bug_968131

Bug 968131 - Tackle intermittent in test_clock_add_alarm_multiple_times

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https://hg.mozilla.org/integration/gaia-central/rev/5bc493bf7b0f
Author: Zac Campbell <zcampbell@mozilla.com>
Desc: Bug 968131 - Tackle intermittent in test_clock_add_alarm_multiple_times
Bumping manifests a=b2g-bump