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

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https://hg.mozilla.org/integration/gaia-1_4/rev/99b2fc404124
Author: Gabriele Svelto <gsvelto@mozilla.com>
Desc: Merge pull request #17762 from gabrielesvelto/bug-989357-recompress-application-icons

Bug 989357 - Recompressed the new application icons r=crdlc,ran
Bumping manifests a=b2g-bump