input/tidal: remove defunct unmaintained plugin

This plugin has been defunct for several years.  Tidal has not ever
replied to any of my emails, so they're apparently not interested in
MPD support.

src/input/InputStream.cxx

@@ -57,7 +57,6 @@ static bool
 ExpensiveSeeking(const char *uri) noexcept
 {
 	return StringStartsWithCaseASCII(uri, "http://") ||
-		StringStartsWithCaseASCII(uri, "tidal://") ||
 		StringStartsWithCaseASCII(uri, "qobuz://") ||
 		StringStartsWithCaseASCII(uri, "https://");
 }