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

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https://hg.mozilla.org/integration/gaia-1_4/rev/790574d89499
Author: Douglas Sherk <github@sherk.me>
Desc: Merge pull request #17540 from DouglasSherk/978814-v1.4

Bug 978814 - [DSDS][Dialer] Re-use currently in-use SIM cards for calls. r=rik

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https://hg.mozilla.org/integration/gaia-1_4/rev/6073964a87b5
Author: DouglasSherk <github@sherk.me>
Desc: Bug 978814 - [DSDS][Dialer] Re-use currently in-use SIM cards for calls. r=rik
Bumping manifests a=b2g-bump