Fixed typo in Opus codec registration

Author: chrisn

opus_codec_registration.src.html

@@ -71,7 +71,7 @@
 AudioDecoderConfig description {#audiodecoderconfig-description}
 ================================================================
 
-{{AudioDecoderConfig/description}} can optionally set to an Identification
+{{AudioDecoderConfig/description}} can be optionally set to an Identification
 Header, described in section 5.1 of [[OPUS-IN-OGG]].
 
 If a {{AudioDecoderConfig/description}} has been set, the bitstream is assumed