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

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https://hg.mozilla.org/integration/gaia-central/rev/40a8306a7319
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Merge pull request #17297 from etiennesegonzac/bug-982196-reflow-helper-upgrade

Bug 982196 - Upgrading the ReflowHelper to use the new devtools tooling.

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https://hg.mozilla.org/integration/gaia-central/rev/21a7faa34a1c
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Bug 982196 - Upgrading the ReflowHelper to use the new devtools tooling.
r=gaye,janx

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https://hg.mozilla.org/integration/gaia-central/rev/cd4d77e23bfe
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Merge pull request #17290 from etiennesegonzac/bug-984882-callscreen-display-l10n-followup

Bug 984882 - 946874 l10n follow up. r=rik

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https://hg.mozilla.org/integration/gaia-central/rev/e03df3a4285f
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Bug 984882 - 946874 l10n follow up. r=rik
Bumping manifests a=b2g-bump