Update vignette text (#6621)

vignettes/datatable-reshape.Rmd

@@ -135,7 +135,7 @@ dcast(DT.m1, family_id ~ ., fun.agg = function(x) sum(!is.na(x)), value.var = "d
 
 Check `?dcast` for other useful arguments and additional examples.
 
-## 2. Limitations in current `melt/dcast` approaches
+## 2. Limitations in previous `melt/dcast` approaches
 
 So far we've seen features of `melt` and `dcast` that are implemented efficiently for `data.table`s, using internal `data.table` machinery (*fast radix ordering*, *binary search* etc.).
 
@@ -170,7 +170,7 @@ str(DT.c1) ## gender column is class IDate now!
 
     As an analogy, imagine you've a closet with four shelves of clothes and you'd like to put together the clothes from shelves 1 and 2 together (in 1), and 3 and 4 together (in 3). What we are doing is more or less to combine all the clothes together, and then split them back on to shelves 1 and 3!
 
-2. The columns to `melt` may be of different types, as in this case (`character` and `integer` types). By `melt`ing them all together, the columns will be coerced in result, as explained by the warning message above and shown from output of `str(DT.c1)`, where `gender` has been converted to *`character`* type.
+2. The columns to `melt` may be of different types. By `melt`ing them all together, the columns will be coerced in result.
 
 3. We are generating an additional column by splitting the `variable` column into two columns, whose purpose is quite cryptic. We do it because we need it for *casting* in the next step.