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

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https://hg.mozilla.org/integration/gaia-central/rev/0518f739c8c0
Author: Zac <zcampbell@mozilla.com>
Desc: Merge pull request #17085 from bebef1987/unxfail

Bug 982178 - Unxfail test_dialer_airplane_mode Bug 978031 is fixed

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https://hg.mozilla.org/integration/gaia-central/rev/fb0ee54bfc6b
Author: Bebe <bebe@mozilla.ro>
Desc: Bug 982178 - Unxfail test_dialer_airplane_mode Bug 978031 is fixed
Bumping manifests a=b2g-bump