fix: encode path in url for aws_sigv4_url/1

[fahchen]

I encountered a SignatureDoesNotMatch when the object key contains characters that need to be escaped, such as spaces or CJK characters.

The path has been encoded at 168L, so we just update the url before returning.

req/lib/req/utils.ex

Line 168 in a3c48b8

path = URI.encode(url.path || "/", &(&1 == ?/ or URI.char_unreserved?(&1)))

[wojtekmach]

Thank you!