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

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https://hg.mozilla.org/integration/gaia-central/rev/5b5b51bdbf87
Author: James Lal <james@lightsofapollo.com>
Desc: Merge pull request #19560 from lightsofapollo/new-tc-images

taskgraph image update

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https://hg.mozilla.org/integration/gaia-central/rev/ab73d41847c5
Author: James Lal <james@lightsofapollo.com>
Desc: NO BUG - taskgraph image update r=me
Bumping manifests a=b2g-bump