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

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https://hg.mozilla.org/integration/gaia-central/rev/58bacf5fd8bb
Author: Zac <zcampbell@mozilla.com>
Desc: Merge pull request #20061 from zacc/bug_1019911

Bug 1019911 - Migrate python tests to vertical homescreen. wait for home...

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https://hg.mozilla.org/integration/gaia-central/rev/b4b25e17c87f
Author: Zac <zcampbell@mozilla.com>
Desc: Bug 1019911 - Migrate python tests to vertical homescreen. wait for homescreen to load in setUp
Bumping manifests a=b2g-bump