Use string instead of int in k8s spec

Summary

I should have tested this, but I missed the fact that the CHANNEL_ID can in most cases be an integer, so we need to force the variable to always be considered a string.

Testing

I tested on this job which definitely wouldn't succeed because there's no such image. This is also ok because the good pokebot image is still there and there's just an adjacent image in imagePullBackoff