flac/vorbiscomment.c : Fix typo.

Patch-from: Jan Stary <hans@stare.cz>
diff --git a/src/flac/vorbiscomment.c b/src/flac/vorbiscomment.c
index 27c6e91..46e8404 100644
--- a/src/flac/vorbiscomment.c
+++ b/src/flac/vorbiscomment.c
@@ -194,7 +194,7 @@
 			 * our previous parsing has already established that the field
 			 * name is OK, so it must be the field value
 			 */
-			*violation = "tag value for is not valid UTF-8";
+			*violation = "tag value is not valid UTF-8";
 			return false;
 		}