[BUGFIX] Fix string repeat
[BUGFIX] Fix string repeat

Used the wrong length for the string repeat technique (needs to be desired length + 1).
Tested this one locally this time.

tildeio/glimmer,glimmerjs/glimmer-vm,tildeio/glimmer,glimmerjs/glimmer-vm,glimmerjs/glimmer-vm,tildeio/glimmer