fix validation to be text instead of string
fix validation to be text instead of string

refs CNVS-21253

test plan
 - subject over 255 char should not error

Change-Id: I0f771f463ff7eecfcdf7132cf78ea78a83c3892f
Reviewed-on: https://gerrit.instructure.com/72962
Reviewed-by: Joel Hough <4816dabf8db1bc6cac35b3a24cab2ff844b5b0c7@instructure.com>
Product-Review: Rob Orton <7e09c9d3e96378bf549fc283fd6e1e5b7014cc33@instructure.com>
QA-Review: Rob Orton <7e09c9d3e96378bf549fc283fd6e1e5b7014cc33@instructure.com>
Tested-by: Rob Orton <7e09c9d3e96378bf549fc283fd6e1e5b7014cc33@instructure.com>

HotChalk/canvas-lms,matematikk-mooc/canvas-lms,venturehive/canvas-lms,matematikk-mooc/canvas-lms,SwinburneOnline/canvas-lms,roxolan/canvas-lms,instructure/canvas-lms,SwinburneOnline/canvas-lms,roxolan/canvas-lms,venturehive/canvas-lms,fronteerio/canvas-lms,sfu/canvas-lms,djbender/canvas-lms,instructure/canvas-lms,grahamb/canvas-lms,grahamb/canvas-lms,sfu/canvas-lms,grahamb/canvas-lms,HotChalk/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,fronteerio/canvas-lms,fronteerio/canvas-lms,HotChalk/canvas-lms,HotChalk/canvas-lms,sfu/canvas-lms,roxolan/canvas-lms,fronteerio/canvas-lms,sfu/canvas-lms,grahamb/canvas-lms,roxolan/canvas-lms,djbender/canvas-lms,venturehive/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,SwinburneOnline/canvas-lms,matematikk-mooc/canvas-lms,SwinburneOnline/canvas-lms,sfu/canvas-lms,dgynn/canvas-lms,sfu/canvas-lms,matematikk-mooc/canvas-lms,dgynn/canvas-lms,grahamb/canvas-lms,dgynn/canvas-lms,djbender/canvas-lms,dgynn/canvas-lms,djbender/canvas-lms,venturehive/canvas-lms