Change string to clarify there is no undo (#1268)
Change string to clarify there is no undo (#1268)


Microsoft/pxt,Microsoft/pxt,switch-education/pxt,Microsoft/pxt,switch-education/pxt,playi/pxt,switch-education/pxt,playi/pxt,switch-education/pxt,playi/pxt,switchinnovations/pxt,switchinnovations/pxt,switchinnovations/pxt,Microsoft/pxt,playi/pxt,switchinnovations/pxt,switch-education/pxt,Microsoft/pxt