rate_compare: `delta = 0` or `delta = delta`?

[jialuo-liu]

https://github.com/Merck/metalite.ae/blob/aab6a5e544942042988fa6ab20661daa3f3d3d1b/R/rate_compare.R#L119C5-L119C15

delta = delta?

[nanxstats]

@elong0527 is this an intended feature or a bug?

I do agree that it is confusing to have a delta argument in rate_compare() while never actually used in the function.