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

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https://hg.mozilla.org/integration/gaia-central/rev/4d91989167da
Author: Francisco Jordano <arcturus@ardeenelinfierno.com>
Desc: Merge pull request #25723 from matarrese/bug-1083733

Bug 1083733 - [Contacts] Contact search higlights more letters than inpu...

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https://hg.mozilla.org/integration/gaia-central/rev/8dd801818f30
Author: Antonio M <matarrese@gmail.com>
Desc: Bug 1083733 - [Contacts] Contact search higlights more letters than input on the search

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https://hg.mozilla.org/integration/gaia-central/rev/9476a31f2338
Author: Guillaume C. Marty <gmarty@users.noreply.github.com>
Desc: Merge pull request #25805 from gmarty/Bug-1090265-Icons-prioritization

Bug 1090265 - Add integration test for icons prioritization

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https://hg.mozilla.org/integration/gaia-central/rev/d40da7004943
Author: Guillaume Marty <edo999@gmail.com>
Desc: Bug 1090265 - Add integration test for icons prioritization
Bumping manifests a=b2g-bump