Fix small typo.

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@14628 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

libavformat/matroska.h

@@ -43,7 +43,7 @@
 #define EBML_ID_VOID               0xEC
 
 /*
- * Matroska element IDs, max. 32 bit
+ * Matroska element IDs, max. 32 bits
  */
 
 /* toplevel segment */