Bumping gaia.json for 1 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/500018386dac
Author: KWierso <kwierso@gmail.com>
Desc: Revert "Merge pull request #26679 from eliperelman/bug-1088118" for linter and gaia-unit test failures

This reverts commit aa5e5c6a81321f2fd1816854cecfeb7646a62fae, reversing
changes made to a7cdad97667823160bb785843e95358b887a5b32.
Bumping manifests a=b2g-bump