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

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https://hg.mozilla.org/integration/gaia-central/rev/21a386e9a9df
Author: viorelaioia <viorela.ioia@softvision.ro>
Desc: Merge pull request #25655 from bebef1987/callscreen

Bug 1091631 - Update CallScreen.reject_call method to wait for the call ...

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https://hg.mozilla.org/integration/gaia-central/rev/3287c556a2a3
Author: Bebe <bebe@mozilla.ro>
Desc: Bug 1091631 - Update CallScreen.reject_call method to wait for the call screen to be not displayed

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https://hg.mozilla.org/integration/gaia-central/rev/99557d05c11a
Author: Marina <marina.rodrigueziglesias@telefonica.com>
Desc: Merge pull request #25581 from gitmai/bug-1089829-usage-add-maxlength-to-data-limit-input

Bug 1089829 - [Usage] Incorrect characters display when setting a data l...
r=salva

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https://hg.mozilla.org/integration/gaia-central/rev/c2ec03ffdf5a
Author: mai <mri@tid.es>
Desc: Bug 1089829 - [Usage] Incorrect characters display when setting a data limit that exceeds 17 characters
Bumping manifests a=b2g-bump