SRI: Remove unnecessary step in "Apply algorithm to resource"

The list of hash functions is already filtered in the "Parse metadata"
algorithm so step 1 will never happen.

Any of the hash functions returned by the "Parse metadata" are
guaranteed to be supported by the user agent or they will not be
added to the `result` list.

It's not wrong to have this step in there, and in fact maybe it was
intentional for clarity, but strictly speaking it's not needed.