mkvmuxerutil::EbmlDateElementSize: remove value param

this is unused as the size of dates is fixed:
Date - signed 8 octets integer in nanoseconds with 0 indicating the
precise beginning of the millennium (at 2001-01-01T00:00:00,000000000
UTC)

Change-Id: I7d44c92a6b746e92e4041238b110115b56e38a93

mkvmuxerutil.cpp

@@ -295,7 +295,7 @@ uint64 EbmlElementSize(uint64 type, const uint8* value, uint64 size) {
   return ebml_size;
 }
 
-uint64 EbmlDateElementSize(uint64 type, int64 value) {
+uint64 EbmlDateElementSize(uint64 type) {
   // Size of EBML ID
   uint64 ebml_size = GetUIntSize(type);