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

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https://hg.mozilla.org/integration/gaia-central/rev/4b9a7652abc6
Author: Michael Henretty <michael.henretty@gmail.com>
Desc: Merge pull request #25670 from mikehenrty/bug-1091645-net-error-fix

Bug 1091645 - Wait for system boot before testing net_error

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https://hg.mozilla.org/integration/gaia-central/rev/7fcf9e77005f
Author: Michael Henretty <michael.henretty@gmail.com>
Desc: Bug 1091645 - Wait for system boot before testing net_error
Bumping manifests a=b2g-bump