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

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https://hg.mozilla.org/integration/gaia-central/rev/c6d57a6a1bcb
Author: Sergi Mansilla <sergi.mansilla@gmail.com>
Desc: Merge pull request #17162 from sergi/976470

Bug 976470 - [Buri][FDN] After entering incorrect PIN 2 code 3 times in resetting PIN2 process, no PUK2 request page

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https://hg.mozilla.org/integration/gaia-central/rev/4f81dca7b513
Author: Sergi Mansilla <sergi.mansilla@gmail.com>
Desc: Bug 976470 - [Buri][FDN] After entering incorrect PIN 2 code 3 times in resetting PIN2 process, no PUK2 request page

The code would not contemplate the possibility of a `lockType` with `'pin2'`, which is actually used by `changePin`.
Bumping manifests a=b2g-bump