Add SoundCloud to the providers not supporting Auth headers

oauth2.go

@@ -287,6 +287,7 @@ func providerAuthHeaderWorks(tokenURL string) bool {
 		strings.HasPrefix(tokenURL, "https://api.instagram.com/") ||
 		strings.HasPrefix(tokenURL, "https://www.douban.com/") ||
 		strings.HasPrefix(tokenURL, "https://api.dropbox.com/") ||
+		strings.HasPrefix(tokenURL, "https://api.soundcloud.com/") ||
 		strings.HasPrefix(tokenURL, "https://www.linkedin.com/") {
 		// Some sites fail to implement the OAuth2 spec fully.
 		return false