According to
https://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.35:

Origin servers that accept byte-range requests MAY send Accept-Ranges:
bytes, but are not required to do so. Clients MAY generate byte-range
requests without having received this header for the resource involved.

Since some servers (e.g. Dell ECS) don't send an `Accept-Ranges: bytes`
header and we are already checking that range requests are supported
when we call `HttpReadSeeker.rangeRequest`, `canSeek` only becomes a
problem and should be removed.

Since it's not clear whether https://github.com/jfbus/httprs is actively
maintained, this commit applies https://github.com/jfbus/httprs/pull/6
to our vendored module.

Closes https://gitlab.com/gitlab-org/gitlab/-/issues/223806