Don't use If-Match header if html was retrieved with `flavor=edit`
Even after merging !103 (merged) (use flavor=edit
for fetching Parsoid HTML with the core API) we still get 412 errors, e.g. with the currently failing doc test. IMO flavor=edit
is not enough, we also have to to remove the If-Match
header to avoid the case that a rendering with that hash is not available.