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

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https://hg.mozilla.org/integration/gaia-central/rev/c560e79619f1
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-central/rev/33917e963157
Author: Fernando Rodriguez Sela <frsela@tid.es>
Desc: Bug 1026377 - [Sora]There is no highlight stripe when selecting some option in STK menu

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https://hg.mozilla.org/integration/gaia-central/rev/8c9c36741908
Author: Timothy Guan-tin Chien <timdream@gmail.com>
Desc: Merge pull request #21251 from timdream/keyboard-cancel-contextmenu

Bug 1028700 - Prevent all contextmenu event on keyboard, r=rudyl

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https://hg.mozilla.org/integration/gaia-central/rev/85092f092798
Author: Timothy Guan-tin Chien <timdream@gmail.com>
Desc: Bug 1028700 - Prevent all contextmenu event on keyboard
Bumping manifests a=b2g-bump