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

========

https://hg.mozilla.org/integration/gaia-central/rev/cd7e66e59ddd
Author: Timothy Guan-tin Chien <timdream@gmail.com>
Desc: Merge pull request #14948 from timdream/keyboard-app-icon

Bug 953032 - Keyboard app needs an icon, r=rudyl

========

https://hg.mozilla.org/integration/gaia-central/rev/9bc75bab47e2
Author: Timothy Guan-tin Chien <timdream@gmail.com>
Desc: Bug 953032 - Keyboard app needs an icon

========

https://hg.mozilla.org/integration/gaia-central/rev/d59f5880db31
Author: George <georgeiscoming@gmail.com>
Desc: Merge pull request #14982 from cctuan/955940

Bug 955940 - [Gaia][Build] Unit Test for install-gaia.js

========

https://hg.mozilla.org/integration/gaia-central/rev/da900cd085ac
Author: cctuan <georgeiscoming@gmail.com>
Desc: Bug 955940 - [Gaia][Build] Unit Test for install-gaia.js