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

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https://hg.mozilla.org/integration/gaia-central/rev/d18c76212021
Author: Greg Weng <snowmantw@gmail.com>
Desc: Merge pull request #20721 from snowmantw/issue1027438

Bug 1027438 - [LockScreen][System] Change the old locking events with ne...

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https://hg.mozilla.org/integration/gaia-central/rev/e2b9d6e8bd11
Author: Greg Weng <snowmantw@gmail.com>
Desc: Bug 1027438 - [LockScreen][System] Change the old locking events with new window events > remove something missed and fork the event
Bumping manifests a=b2g-bump