Fix md.features and data.features comparison

[neanderthalensis]

When trying to run UpdateSeuratObject on this dataset I got the following error message: Error in !all.equal(target = md.features, current = data.features, check.attributes = FALSE) : invalid argument type

all.equal returns true if md.features and data.features are indeed identical. However in case where the two vectors differ it returns a character vector of length two describing the mismatch. For the RNA slot in the above dataset it returns:

[1] "Lengths (463, 461) differ (string compare on first 461)"
[2] "8 string mismatches" 

The proposed change simply replaces all.equal() with identical() which should be more suitable as it will simply determine if the two vectors are identical and returns a boolean which can then be used by the if statement.