Bumping gaia.json for 2 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/5fd2221990ca
Author: Min-Zhong "John" Lu <jlu@mozilla.com>
Desc: Merge pull request #25249 from mnjul/bug_1075306_input_window_stage3

Bug 1075306 - Implement InputWindow (inherits from AppWindow). r=zac,timdream,alivedise,rudyl

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https://hg.mozilla.org/integration/gaia-central/rev/31705ebcb5c1
Author: John Lu [:mnjul] <jlu@mozilla.com>
Desc: Bug 1075306 - Implement InputWindow (inherits from AppWindow)

- Instances of InputWindow replaces those iframes we were keeping in InputFrameManager.
- InputAppTransitionManager has been eliminated, in favor of already-built AppTransitionController that works closely with AppWindow.
- The coupling of KeyboardManager, InputFrameManager and InputWindows shall be resolved in a following bug where we'll implement InputWindowManager.
- Flow of showing/hiding/reusing/switching input apps & layouts has been streamlined.
Bumping manifests a=b2g-bump