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

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https://hg.mozilla.org/integration/gaia-central/rev/38ce454dc452
Author: Michael Henretty <michael.henretty@gmail.com>
Desc: Merge pull request #17398 from zacc/bug_986117

Bug 986117 - Debug intermittents in test_settings_app_permissions.py, r=mhenretty

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https://hg.mozilla.org/integration/gaia-central/rev/7cd0d3ae228b
Author: Zac <zcampbell@mozilla.com>
Desc: Bug 986117 - Resolve intermittents in test_settings_app_permissions.py with enhanced wait for Settings app initialisation r=mhenrtty
Bumping manifests a=b2g-bump