i18n: fix typo in excluded key
i18n: fix typo in excluded key

refs FOO-1614
flag = none

test plan: `bundle exec rake i18n:generate` does not include any values
like `!ruby/object:Proc {}`

Change-Id: I5013f759f5274573e60264e6aa844fabff6a7ad6
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/259241
Reviewed-by: Ahmad Amireh <a53a33601b8dd9d06ae9e50f1f30fbe957aba866@instructure.com>
QA-Review: Ahmad Amireh <a53a33601b8dd9d06ae9e50f1f30fbe957aba866@instructure.com>
Product-Review: Ahmad Amireh <a53a33601b8dd9d06ae9e50f1f30fbe957aba866@instructure.com>
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>

instructure/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,instructure/canvas-lms