Remove 'low-delay' from the pkg-config description.

While a feature of Opus, its applications are not limited
to contexts where low delay is important.

opus.pc.in

@@ -6,7 +6,7 @@ libdir=@libdir@
 includedir=@includedir@
 
 Name: Opus
-Description: Opus IETF low-latency audio codec
+Description: Opus IETF audio codec
 URL: http://opus-codec.org/
 Version: @VERSION@
 Requires: