update th translation
update th translation

Change-Id: Icfb01c7fa98fb8285bc9d52a259004d1982ba788
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/298743
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>

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