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

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https://hg.mozilla.org/integration/gaia-central/rev/4f848b944d55
Author: gasolin <gasolin@gmail.com>
Desc: Merge pull request #18617 from gasolin/issue-959983

Bug 959983 - NFC: There should be an icon for NFC on the status bar, r=alive

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https://hg.mozilla.org/integration/gaia-central/rev/6d70a4778361
Author: gasolin <gasolin@gmail.com>
Desc: Bug 959983 - NFC: There should be an icon for NFC on the status bar

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https://hg.mozilla.org/integration/gaia-central/rev/3c74f78e0ff7
Author: Staś Małolepszy <stas@mozilla.com>
Desc: Merge pull request #18789 from stasm/1003184-fm-langdir

Bug 1003184 - Don't set document's lang and dir in FMRadio. r=pzhang

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https://hg.mozilla.org/integration/gaia-central/rev/2a9ea6bb1f9b
Author: Staś Małolepszy <stas@mozilla.com>
Desc: Bug 1003184 - Don't set document's lang and dir in FMRadio. r=pzhang
Bumping manifests a=b2g-bump