mapply is hard for CSAMA attendees

[mikelove]

I often get students confused by this part. Recommend removing as we don't teach mapply().

CSAMA-labs/intro-to-r-bioc/L1.4-bioc-data-representation.Rmd

Lines 136 to 146 in 92bc693

	Explain what the following code does, and how it works
	```{r consensusMatrix}
	m <- consensusMatrix(phiX174Phage)[1:4,]
	polymorphic <- which(colSums(m != 0) > 1)
	mapply(
	substr,
	start = polymorphic, stop = polymorphic,
	MoreArgs=list(x=phiX174Phage)
	)
	```