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

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https://hg.mozilla.org/integration/gaia-2_1/rev/f46d4715135e
Author: Ghislain 'Aus' Lacroix <aus@noiseport.org>
Desc: Merge pull request #24354 from nullaus/bug1064975

bug 1064975 - ensure enter/leaveTaskManager is called for *all* applicat...

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https://hg.mozilla.org/integration/gaia-2_1/rev/7502e772e794
Author: Ghislain 'Aus' Lacroix <aus@mozilla.com>
Desc: bug 1064975 - ensure enter/leaveTaskManager is called for *all* applications even when stack is filtered. r=sfoster

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https://hg.mozilla.org/integration/gaia-2_1/rev/4bce0496a39d
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 1071707 - Remove browser dependency from marionette tests r=Cwiiis
Bumping manifests a=b2g-bump