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

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https://hg.mozilla.org/integration/gaia-1_4/rev/84c1ea23a2b9
Author: Min-Zhong "John" Lu <mnjul@users.noreply.github.com>
Desc: Merge pull request #20468 from mnjul/v1.4

Revert "Merge pull request #20058 from mnjul/bug_1011645_lockscreen_passcode_camera_button_stall_v1.4"

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https://hg.mozilla.org/integration/gaia-1_4/rev/747fbceca828
Author: John Lu [:mnjul] <jlu@mozilla.com>
Desc: Revert "Merge pull request #20058 from mnjul/bug_1011645_lockscreen_passcode_camera_button_stall_v1.4"

This reverts commit 8b239e41bbd85aa7b6a2c5d388e775ba7de6fb2b, reversing
changes made to 83cae7b7510fc837e27ecd0e298aa462e61f7761.
Bumping manifests a=b2g-bump