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

========

https://hg.mozilla.org/integration/gaia-central/rev/23df3aeef9e1
Author: Sergi Mansilla <sergi.mansilla@gmail.com>
Desc: Merge pull request #16831 from sergi/921971-fdn

Bug 921971 - [DSDS][FDN] Manage FDN list for both SIMs

========

https://hg.mozilla.org/integration/gaia-central/rev/fcd18131ccc6
Author: Sergi Mansilla <sergi@Sergis-MacBook-Pro.local>
Desc: Bug 921971 - [DSDS][FDN] Manage FDN list for both SIMs

This fix makes it possible to have independent Fixed Dialing Numbers for each
SIM card in the phone. A new function `getIccByIndex` has been introduced in
`utils.js` that selects the currently selected ICC object without the user
having to specify the particular index, although it allows that too (used in
`sim_dialog.js`, for example.

Instances of `IccHelper` have been replaced by the result of calls to
`getIccByIndex`.
Bumping manifests a=b2g-bump