[Rd] Typo in the man page of ?cutree (PR#14223)

[phgrosjean at sciviews.org]

In the examples section of ?cutree (stats package):

hc <- hclust(dist(USArrests))

cutree(hc, k=1:5)#k = 1 is trivial
cutree(hc, h=250)

## Compare the 2 and 3 grouping: <<= SHOULD READ AS: "2 and 4 grouping"
g24 <- cutree(hc, k = c(2,4))
table(g24[,"2"], g24[,"4"])