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

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https://hg.mozilla.org/integration/gaia-1_4/rev/b9a7521f416f
Author: Ben Tian <btian@mozilla.com>
Desc: Merge pull request #20723 from bentian/bug-1026475-14

Bug 1026475 - Device switch from Handset/Headset to BTSCO fails during call, r=etienne, a=1.4+

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https://hg.mozilla.org/integration/gaia-1_4/rev/aea2f0534ed2
Author: Ben Tian <btian@mozilla.com>
Desc: Bug 1026475 - Device switch from Handset/Headset to BTSCO fails during call, r=etienne, a=1.4+
Bumping manifests a=b2g-bump