Bumping gaia.json for 1 gaia-1_2 revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-1_2/rev/975340e51a5a
Author: Anthony Ricaud <anthony@ricaud.me>
Desc: Merge pull request #12462 from dwi2/bug911010

Bug 911010 - [B2G][Helix][dialer][tongxiao]The emergency call Interface ... r=rik
(cherry picked from commit c3bb0282f306cfbb4112aedb835d676f4a965127)