Bumping gaia.json for 4 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/b424e91a5612
Author: Jan Keromnes <janx@linux.com>
Desc: Merge pull request #17801 from jankeromnes/disintegrate

Bug 989272 - FPS and TTL monitors shouldn't depend on the Developer HUD being active. r=21

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https://hg.mozilla.org/integration/gaia-central/rev/d6a6f45b62cf
Author: Jan Keromnes <janx@linux.com>
Desc: Bug 989272 - FPS and TTL monitors shouldn't depend on the Developer HUD being active. r=evelyn

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https://hg.mozilla.org/integration/gaia-central/rev/c8eaa87764b1
Author: Jan Keromnes <janx@linux.com>
Desc: Merge pull request #17983 from jankeromnes/feura

Bug 992216 - s/Feura/Fira/. r=21

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https://hg.mozilla.org/integration/gaia-central/rev/a9de75c35ec6
Author: Jan Keromnes <janx@linux.com>
Desc: Bug 992216 - s/Feura/Fira/. r=21
Bumping manifests a=b2g-bump