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

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https://hg.mozilla.org/integration/gaia-central/rev/7ecc490551fe
Author: David Flanagan <dflanagan@mozilla.com>
Desc: Merge pull request #15702 from davidflanagan/bug959049

Bug 959049: reduce keyboard row height and font-size in landscape mode

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https://hg.mozilla.org/integration/gaia-central/rev/673245f360bd
Author: David Flanagan <dflanagan@mozilla.com>
Desc: Bug 959049: reduce keyboard row height and font-size in landscape mode

fix the size of the word suggestion area, too

change so JS doesn't need to know anything about the definition of 1rem
Bumping manifests a=b2g-bump