Bumping gaia.json for 3 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-1_4/rev/81d4c24aecc7
Author: Fernando Rodríguez Sela <frsela@tid.es>
Desc: Merge pull request #20781 from frsela/STK/Bug1026377

Bug 1026377 - [Sora]There is no highlight stripe when selecting some option in STK menu, r=jaoo

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https://hg.mozilla.org/integration/gaia-1_4/rev/537ec7e3434b
Author: Ryan VanderMeulen <rvandermeulen@mozilla.com>
Desc: Merge pull request #21320 from alivedise/bugzilla/996141_v1.4/activity-window-should-not-hide-its-caller

Bug 996141 - Put in-proc app in foreground when it invokes activity

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https://hg.mozilla.org/integration/gaia-1_4/rev/a6080dd0485a
Author: Alive Kuo <alegnadise@gmail.com>
Desc: Bug 996141 - Put in-proc app in foreground when it invokes activity
Bumping manifests a=b2g-bump